As well as running one of the world's largest cities, Boris Johnson has to field requests for everything from his favourite recipe to joining Army paratroopers on a skydive.

The London Mayor's correspondence ranges from a plea for "Boris bikes" for district nurses to an inquiry from a survivor of the 7/7 terrorist attacks wanting to be involved in the 2012 Olympics.

His inbox also contains a mixture of fan mail - one writer praises his "straight-to-the-point and believable attitude" and concludes "hopefully (we) will see you some day at No 10" - and trenchant criticism.

Copies of emails sent to and from Mr Johnson's official City Hall account, obtained through a Freedom of Information request, show how his office takes an interest in the minutiae of public services across the capital.

On September 10 2010 the Mayor responded to a request for accredited buskers to be allowed to sell CDs and other merchandise in Tube stations, saying that London Underground was "unlikely" to allow the move.

But he was more positive about a suggestion that extra docking stations for his bicycle-hire scheme, nicknamed "Boris bikes", be installed in locations convenient for district nurses in Islington, north London.

A week later he reassured a resident of Stonecot Hill, south London, that Transport for London had taken steps to stop a CCTV camera from filming their house.

The messages demonstrate how Mr Johnson has divided public opinion since his election in May 2008.

In September 2008, a supporter from Northern Ireland wrote to the London Mayor: "Of late I have come to admire your straight-to- the-point and believable attitude that you put across with the greatest of ease and in such a unique and fun fashion...

"I... can only dream of someone somewhere entering into local politics here with the Boris attitude and help make a difference.

"I look forward to seeing you go from strength to strength, and hopefully will see you some day at No 10 and we will then finally have a PM that is worth his salt."

Another correspondent said a visiting German exchange student was "VERY impressed" by a trip to London because "everywhere was clean, no rubbish, there were no drunks on the Tube, there were no homeless people sleeping in the streets or doorways".

But that same month a critic wrote to the Mayor: "Dear Boris, please resign. You (are) clever and funny and that, but to be honest, it ain't enough. You are a bad Mayor and should leave quickly...

"All the best in your new job (so long as it doesn't involve power or the UK)."

The emails give an insight into Mr Johnson's hectic schedule. The phrase "I am alas snowed under, and mustn't take anything else on at the moment" features in a number of his replies.

In September 2010 he had to turn down an offer to take part in a tandem skydive with the Red Devils, the Parachute Regiment's freefall display team, writing: "Much as I appreciate the invitation it is not possible for me to accept."

And in July this year he said he had no time to meet Big Issue founder John Bird to discuss London's homelessness problem, and declined to pose for a budding photographer.

But the correspondence makes it clear that Mr Johnson does his best to oblige those who write to him.

Responding to a questionnaire about London and his role, he said being Mayor was "very, very difficult" but "easily the best job I have ever had".

In July this year he wrote back to a 7/7 survivor who was on the double-decker bus bombed in Tavistock Square offering a pair of VIP tickets to the concert he is staging on the night of the Olympics opening ceremony on July 27.

Among the emails is a message sent by a parent in Putney, west London, asking Mr Johnson to contribute his favourite recipe for a Christmas cookbook to raise funds for their daughter's school. The reply is not included.