Wimbledon's Unsung Hero

You've watched my work in your millions every year without fail, as I'm on the screen so frequently; and yet few know my face; that's how I'd like it: do your job, go watch the game... there's some doubt whether I do this just for love; or whether money changes hands in some offshore account; or indeed, whether I'm a conspiracy involving the better-known; the less known, the better, is what I say; who wants the dread words 'product placement' bandied around this hallowed turf.. but yes, you've guessed it: I'm the guy you never see who turns the labels on the Robinson's bottles (once of barley-water fame, in the days before 'probiotic liquid supplements') to face the TV camera.. my service never faults.