Felt his collar

For me at least, this expression initially conjured up images of Bow Street runners chasing down ne’er do wells on the murky streets of Victorian London. When setting out to research the phrase I expected to find it in Dickens or the like. Actually, it turns out to be a much more recent coinage than that. The first example that I can find of it is in the English author Paul Tempest’s Lag’s Lexicon a Comprehensive Dictionary and Encyclopedia of the English Prison of to Day, 1950:

To ‘get your collar felt (or touched)’ is to be arrested or stopped by the police.

‘I’ll feel his collar’ was often used by characters in hard-boiled London-based TV police dramas of the 1970s, like The Sweeney and The Professionals. It quickly became well enough established that, in those shows and now in real life, an arrest became known as a collar.

Confusingly, there was already a type of draft horse harness called a Sweeney Collar. This is just a coincidence and not the source of the name of the TV show. That name is Cockney Rhyming Slang – Flying Squad -> Sweeney Todd.