A gay man was lured into a meeting through the dating app Grindr and then robbed and threatened with a cattle prod.
Detectives have released CCTV pictures of two men they are hunting in connection with the attack - and warned the culprits could have targeted others.
Scotland Yard said the man, 26, had been messaging a man through the popular online gay dating app Grindr and invited him round to his home in Bayswater, west London.
When the man, described as blond and in his 20s, arrived he spent most of his time texting on his phone and then announced he was leaving and was escorted out by the victim.
But his accomplice was lying in wait outside wielding a cattle prod, and when the front door opened the pair pounced on the victim, pushing him into his flat.
They threatened him with the cattle prod and stole cash and a laptop computer before fleeing the home in Queensborough Terrace.
The victim, who has not been named, did not suffer serious injuries but was "very shaken" by the attack, which happened at around 5pm on September 28.
Detective Constable April Smart, of Westminster CID, said: "The victim thankfully did not suffer serious physical injuries but has been left very shaken by this incident.
"I am keen to identify the two suspects as soon as possible and I am appealing to anyone who may know who they are to contact the police.
"Whilst we have not connected this incident to any other reported to us, I must consider that the suspects could have committed this type of offence previously and I would appeal to anyone who may have been a victim of this type of offence to contact the police, where they will be treated with the utmost sensitivity.
"I would like to take this opportunity to reassure the LGBT (lesbian, gay, bisexual and transgender) community that we are doing everything we can to arrest these men and have followed and eliminated a number of potential leads and inquiries to date.
"I would urge everyone who uses the services of online dating apps and sites to take steps to help them to stay safe whilst meeting strangers."
The first suspect is described as white, of slim build and in his mid-20s with short blond hair.
The second suspect is described as white, in his late 20s, of medium build and bald.
Police are asking anyone with information to contact them on 020 7321 7513, or to call Crimestoppers anonymously on 0800 555 111.