He has faced verbal abuse, jostling and spitting since he arrived at the Edinburgh Festival Fringe to perform an anti-racist play, My England, about football hooliganism. So far, audiences have been polite; it is in the street that Mr Salt has run into trouble.
Along with hundreds of other performers he goes out to drum up custom on the Royal Mile in costume, wearing St George's Cross face make-up and with an England flag knotted around his shoulders.
Some Scots have taken him literally. "I get banter - things like 'Brazil 2:1' chanted, I've been jostled and shouted at, including by a group of 14-year-old girls who were very abusive, and even spat at me. The worst was the other day when a guy said 'Your flag is shite. I'd like to put a knife through your heart.' That was quite frightening."
Mr Salt was accompanied at the time by black actor Willan Ferguson, also in the play, so there could be no suggestion he sympathised with the British National Party.
Until the end of term Mr Salt taught German at St Peter's school in Huntingdon, Cambridgeshire. He says he has found it instructive to play a character who describes being told off by a teacher about his haircut. "Ant (the England fan) has never been treated with respect." This is where the seeds of his anti-social behaviour lie.
The play is endorsed by the Show Racism a Red Card campaign, and is the third in a series of pieces that aims to combat racism in football. It counts FIFA and the Scottish Professional Footballers' Association among its sponsors.
But another sponsor, Railtrack, has decided not to put up posters at Edinburgh's Waverley Station.
My England has been shortlisted for an Amnesty International Freedom of Expression Award.