A selfie with Boris Johnson cost one commuter his laptop and his life's work.
Tibetan-born Lelung Rinpoche, 43, was travelling on the Tube with his two-year-old son when he asked the Mayor of London for a selfie.
After leaving the Metropolitan line train a few stops later, the religious teacher soon realised that he had left his bag containing his laptop behind.
"I had just been to register the birth of my baby girl Tenzing and when I got back to the Tube I saw Boris just a few feet away," the father-of-two from Pinner explained.
"I thought, OK I should take my son and get a photo with Boris as a memento in case my son is interested when he is older."
He said he discussed Tibet with the conservative politician who expressed a desire to visit the area.
However, his joy was short-lived when he realised his mistake.
"Before I realised I had lost my bag I was very, very happy because I had met Boris.
"But as soon as I found out it had gone I was very worried. I am going to have to work twice as hard to re-write my work," he said.
After contacting London Underground, he discovered someone had handed in his bag with his keys and camera still in it, but his laptop - containing three years worth of Tibetan scriptures and poems - had disappeared.
Mr Rinpoche's employers, the Buddhist teaching charity the Lelung Dharma Trust, are offering a £500 reward to anyone who can hand the laptop in, and the 43-year-old insists the mayor can help with the search
"I don't wish any ill feeling on the person who took it, I just want them to come forward.
"It is not worth very much money - it is just an old computer. But it is priceless to me.
"It would be great if Boris Johnson could help me in my appeal to try to find it."