A single social media post turned what had been one of Syed Usman Shah's "proudest moments" into one of the most overwhelming and upsetting. It started when Shah, 35, was approached by Heathrow Airport to be part of their "Welcome" campaign. The airport selected 38 successful Londoners whose smiling, waving images would be used on large posters at Heathrow to welcome visitors to the city. Those chosen included a Beefeater, a Wimbledon umpire and others with prominent London jobs or who worked at tourist spots. Shah's poster shows him waving while holding a small basket of dates in his other hand. That is because he's an entrepreneur and owner of The Date Sultan stand at London's Borough Market, where he sells fair-trade dates. He leapt at the chance to become one of the faces of the Heathrow campaign and describes the moment his parents saw the posters at the airport as "one of the highlights of my life". "For me, it was a pinch-me moment," says Shah.…