A dating website for married people seeking illicit affairs has revealed a new trend among its female users.

Since its launch in 2009, Undercoverlovers.com noted that most women on the site wanted to hook up with an older man (while male members were predictably searching for younger lovers).

However since the beginning of 2012, more than 50% of the site's female members now look for younger guys to cheat with.

The website researched the profiles of all of its 663,000 members to ascertain their age when they joined and stated age preference for an affair partner.

Undercover Lovers spokesperson Emily Pope comments: 'We are surprised to note this new trend on our site."

"Middle-aged Hollywood film director Rupert Sanders and Anthea Turner's husband Grant Bovey, both of whom are currently in the news for their alleged indiscretions with 20somethings, are just the latest high profile examples of the historical norm."

Did you know these celebrities also couldn't resist the allure of their colleagues?

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• Angelina Jolie and Brad Pitt

  In 2004, rumors surfaced that co-stars Brad Pitt and Angelina Jolie were doing more than just acting on the set of the action flick "Mr. & Mrs. Smith." Pitt, who was married to Jennifer Aniston at the time, would go on to <a href="http://www.justjared.com/2009/01/07/brad-pitt-denies-angelina-jolie-affair/" target="_hplink">deny the affair allegations</a>, as did <a href="http://www.people.com/people/article/0,,20004139,00.html" target="_hplink">Jolie</a>, but tabloid reports continued nonetheless. In March 2005, <a href="http://www.people.com/people/article/0,,1042412,00.html" target="_hplink">Aniston filed for divorce</a> from Pitt. Still, Jolie raised eyebrows again in October 2008, when she told the <em>New York TImes </em>that she <a href="http://today.msnbc.msn.com/id/27242037/ns/today-entertainment/t/brangelina-affair-started-mr-mrs-smith/#.UBA4dzHLyRk" target="_hplink">looks forward to the day her six children with Pitt can watch "Mr. & Mrs. Smith."</a> "Not a lot of people get to see a movie where their parents fell in love," Jolie said.

• Elizabeth Taylor and Richard Burton

  Before there was Brangelina, there was Elizabeth Taylor and Richard Burton. Screen siren Taylor famously took up with British thespian Burton while filming 1963's "Cleopatra." The only problem? Both were married at the time -- Taylor to fourth husband Eddie Fisher and Burton to Sybil Williams, <a href="http://news.google.com/newspapers?nid=1957&dat=19920621&id=4GZGAAAAIBAJ&sjid=3OgMAAAAIBAJ&pg=4546,5429384" target="_hplink">his wife of fourteen years</a>. On March 15, 1964, just <a href="http://news.google.com/newspapers?id=wwIqAAAAIBAJ&sjid=ZicEAAAAIBAJ&pg=7447,4620597&dq=elizabeth+taylor+marries+richard+burton&hl=en" target="_hplink">nine days after her divorce from Fisher was finalized</a>, Taylor made Burton her fifth husband. The couple divorced in 1974, <a href="http://www.huffingtonpost.com/2011/03/23/elizabeth-taylor-divorce_n_839611.html" target="_hplink">remarried in 1975</a> and finally divorced for good the following year.

• Ingrid Bergman and Roberto Rossellini

  Academy Award-winning actress Ingrid Bergman was married to Petter Lindström, with whom she had a daughter, when she landed a role in Italian director <a href="http://www.tcm.com/this-month/article/60080%7C0/Stromboli.html" target="_hplink">Roberto Rossellini's film "Stromboli" in 1950</a>. During production, which took place in Italy, <a href="http://www.tcm.com/this-month/article/60080%7C0/Stromboli.html" target="_hplink">she fell in love with Rossellini</a>, who was also married at the time, and became pregnant with their son. A scandal ensued, culminating in <a href="http://www.tcm.com/tcmdb/person/14558%7C72764/Ingrid-Bergman/biography.html" target="_hplink">Bergman being denounced</a> by the U.S. Congress and virtually blacklisted by the U.S. film industry. <a href="http://www.huffingtonpost.com/2011/05/21/arnold-schwarzenegger-hollywood-scandals_n_864932.html#s281464&title=Fatty_Arbuckle" target="_hplink">"Hollywood wouldn't touch her,"</a> said James Robert Parish, the author of "The Hollywood Book of Scandals." Bergman and Rosselini married in May 1950 and later had twin daughters, but they didn't return to Hollywood <a href="http://thehairpin.com/2011/04/scandals-of-classic-hollywood-ingrid-bergman-instrument-of-evil/" target="_hplink">until the late '50s</a>.

• Jennifer Lopez and Ben Affleck

  Ben Affleck and Jennifer Lopez, also known as "Bennifer", <a href="http://www.usatoday.com/life/people/2004-01-23-bennifer-timelilne_x.htm" target="_hplink">met on the set of box-office bomb "Gigli" in early 2002</a>, while Lopez was married to her second husband, Cris Judd. Three days before Lopez filed to divorce Judd in July 2002, <em>People</em> reported that the actress was <a href="http://www.people.com/people/archive/article/0,,20137732,00.html" target="_hplink">already introducing Affleck as her "new boyfriend" to friends</a>. Though the couple became engaged in November 2002, in the end, Bennifer couldn't stand the test of time; by January 2004, <a href="http://www.usatoday.com/life/people/2004-01-22-bennifer-breakup_x.htm" target="_hplink">the relationship was over for good.</a>

• Meg Ryan and Russell Crowe

  In July 2000, Meg Ryan and Dennis Quaid <a href="http://www.ew.com/ew/article/0,,276771,00.html" target="_hplink">announced they were separating</a> amid allegations of an affair between Ryan and her "Proof of Life" co-star Russell Crowe. A month before the filing, Ryan and Crowe (pictured here with director Taylor Hackford) were <a href="http://www.people.com/people/archive/article/0,,20131801,00.html" target="_hplink">reportedly seen "cuddling, hugging, kissing" on set</a>. Quaid and Ryan's <a href="http://blog.sfgate.com/dailydish/2008/09/29/quaid-denies-ryan-is-moving-for-full-custody-of-son/" target="_hplink">divorce was finalized in 2001</a>. Meanwhile, the actress' relationship with Crowe reportedly <a href="http://www.usmagazine.com/celebrity-news/pictures/stars-caught-cheating-2009318/2771" target="_hplink">fizzled out after a few months</a>.

• Humphrey Bogart and Lauren Bacall

  Humphrey Bogart was 44 and married to Mayo Methot when he met and fell for 19-year-old <a href="http://books.google.com/books?id=zlSRS80XIfQC&pg=PT642&lpg=PT642&dq="To+Have+and+Have+Not"+"married+to+Mayo+Methot"&source=bl&ots=iIBF1o-Vfi&sig=6-yaGWpuYckWqpBwEIGtuYiUaLs&hl=en&sa=X&ei=I0oQUK7lAu3siwKq34GIDg&ved=0CEwQ6AEwAjgK#v=onepage&q="To Have and Have Not" "married to Mayo Methot"&f=false" target="_hplink">Lauren Bacall weeks into shooting 1944's "To Have And Have Not."</a> Within months, Bogart <a href="http://www.biography.com/people/lauren-bacall-9194111" target="_hplink">divorced Methot and married</a> Bacall in May 1945. The pair remained married until <a href="http://entertainment.time.com/2012/07/06/reel-love-top-10-movies-that-begat-off-screen-romances/slide/to-have-and-have-not/#to-have-and-have-not#ixzz21fTjc7Nw" target="_hplink">Bogart's death, from esophageal cancer</a>, in 1957.

• Penelope Cruz and Tom Cruise

  Soon after his split from Nicole Kidman, Tom Cruise co-starred with Penelope Cruz in Vanilla Sky, and before long she was on his arm in real life, too. Director Cameron Crowe was delighted with this development, saying it was wonderful "watching them fall in love in front of your eyes". And the additional publicity for the film didn't hurt either.

• Tom Cruise and Nicole Kidman

  What goes around... Tom Cruise was married to Mimi Rogers when he met Nicole Kidman on the set of <em>Days of Thunder</em>. With Cruise-like calmness, he announced to Mimi, "I'm with Nicole now."

• Kenneth Branagh and Helena Bonham Carter

  After his divorce from Emma Thompson, Kenneth Branagh was in a relationship with Helena Bonham Carter, whom he directed and starred with in <em>Mary Shelley's Frankenstein.</em>

• Brad Pitt and Gwyneth Paltrow

  Before he was swept into Angelina's arms, Brad Pitt and Gwyneth Paltrow were almost identical in appearance, having teamed up on the set of thriller <em>Seven</em>.

• Angelina Jolie and Billy Bob Thornton

  And long before she caused such ripples in the Aniston-Pitt household, Angelina Jolie was causing simliar challenges on the set of <em>Pushing Tin</em>, where she met Billy Bob Thornton. Soon they were swapping vials of each other's blood, and his marriage to Laura Dern was over.

• Jennifer Aniston and Vince Vaughn

  After she split from Brad Pitt, Jennifer Aniston found solace in the arms of her <em>Break Up</em> co-star Vince Vaughn. "He brought me back to life," she said afterwards.

• Rachel Weisz and Daniel Craig

  Both were with other people in long term relationships, but the long-standing friendship between Rachel Weisz and Daniel Craig turned to love on the set of <em>The Dream House</em>, and they were married within the year.

• Jennifer Aniston and Justin Theroux

  Jennifer Aniston again... she obviously spends a lot of time working... this time on the set of <em>Wanderlust</em>, where she met co-star Justin Theroux. The pair have been inseparable ever since, and Ms Aniston appears to have even slowed down her work rate.

• Kate Beckinsale and Len Wiseman

  Things got sticky on the set of Waterworld, when star Michael Sheen's partner and co-star Kate Beckinsale fell for their director Len Wiseman. Being British, this was all handled with impeccable civility, and the three all live in Los Angeles, so that both parents can share the upbringing of their daughter Lily.

• Emma Stone and Andrew Garfield

  Although they have never publicly admitted their relationship, the chemistry between Emma Stone and <em>Spiderman</em> co-star Andrew Garfield was evident both on screen and during the ensuing worldwide junket - oh, and in pictures of them kissing their way around New York.

• Anna Friel and Rhys Ifans

  Rhys Ifans, lovelorn after being dumped by Sienna Miller, found solace with his <em>Neverland</em> co-star Anna Friel.

She continues: "'The spate of 'cougar' media stories over recent months, such as married, 32-year-old radio DJ Lucy Horobin's conquest of teenage, One Direction band member Harry Styles, may be indicative of the new trend we've identified, or inspiring our female members to seek out a younger stud."

Relationship expert and psychologist Dr Amelie Duval is not surprised by the survey results however.

"Men generally hit their sexual peak in their 20s, while with women it's much later, in their late 30s or early 40s. It's small wonder then that older married women, many of whom will have already had their children and seen them fly the nest, should seek sexual and emotional excitement with a younger lover if they're not feeling fulfilled at home."

Undercover Lovers member Mary, a married 45-year-old physiotherapist from Essex, is secretly dating Tom, a 34-year-old City trader.

She says: 'My much older husband provides me with all of the safety and security I need but none of the excitement in bed. With my young lover Tom I bring experience, wisdom and spice to the relationship whilst he brings youthful energy and sexual staying power!'

Would you know if your partner was having an affair?

• Signs Of Lying

• Eyes

  Watch out for an avoidance of eye contact or eyes moving too quickly

• Smug

  Do they look more 'smug' than normal?

• Calm

  Are they displaying high levels of 'calm'?

• Shrugging

  Are their words accompanied with frequent 'small shrugs'?

• Hair

  Do they play with their hair while talking?

• Smile

  Does their smile reach all the way to their eyes?

• Obstacle

  Does this person deliberately place an object/piece of furniture between you and them while talking?

• Sweat

  Are they sweating more than normal?

• Face

  Do they touch their face while talking?

The majority of UndercoverLovers.com members are in their 30s and 40s. In the years 2009-2011, 83% of the site's male members were seeking younger lovers, whilst only 36% of female members expressed a preference for a younger man.

Since the beginning of 2012, 52% of women now wish to find partners younger than themselves whilst the figure for men has remained more or less consistent at 84%.

See Also:

• Why Women Are More Likely To Cheat When It's Raining
• Quarter Of Women Admit To Infidelity With Work Colleague