"I'm a grammar vigilante," he told the BBC. "I do think it's a cause worth pursuing. I have felt extremely nervous. The heart has been thumping." He claims to visit different high streets across the city, using a trestle for the harder-to-reach banners in order to make good on his name. One of his most recent corrections was to Cambridge Motor's garage, where an errant apostrophe in "Motor's" had annoyed him for years. It isn't the first time the vehicle repairs service has suffered at his hands. Paul, who manages Cambridge Motor's, said he caught the man in the act more than two years ago, when he was seen attempting to scrub out an apostrophe on a sign that read "Keys and letter's through here". "We put up a sign and I caught him at the front attempting to scrub off permanent marker," he told The Telegraph.

"I said to him, 'What are you doing?' and he said, 'You've got a rogue apostrophe there.' He was a middle-aged bloke, he obviously lives locally and it's just his pastime." While Paul is more than happy for the grammarian to point out mistakes, many are less receptive. Jason Singh, 42, who owns the tailors Tux & Tails, claims that he potentially faces paying thousands of pounds for his sign to be corrected. The issue, the omission of an apostrophe in "Gentlemens", has been corrected with what appears to be two blobs of paint, or stickers, that do not sit well with the newly-fitted vinyl.

"I did take it lightly at first, but now I'm a little angry to be honest," he said. "We think it's paint, and this is vinyl, so if we have to replace it you're looking at a few thousand pounds. I understand, but at the end of the day I'd have preferred him to come in and tell me. "I think it could be considered rather rude. I think there might even be grounds for a police complaint, and if his name is revealed, I'll be sending him an invoice for the damages." However, the vigilante has defended the legality of his work, telling reporters that some of the mistakes he redresses are "just wrong" and that "it's more of a crime to have apostrophes wrong in the first place". Melania Branton, a poet from North Somerset, said that whoever the "grammar vigilante" turns out to be "must be wincing at the misnomer, as punctuation isn't grammar". Meanwhile, Peter Barker, the chairman of the Queen's English Society, added: "I don't disapprove of his motives; in fact, I can see why he would be frustrated. Whether or not I would be going about his business late at night is another matter, however."

A spokesman for Avon and Somerset Police said the force was unaware of any complaints being lodged, but any permanent damage caused could provide grounds for police intervention. Telegraph, London