restricting bets

What sports/events were you betting on?

They`re not trying to nick £200 of every mug, then, in effect, close the account, happy with the one-off £200
Nor has it anything to do with `what` you`re betting on.
It`s entirely down to `how` you bet, your betting patterns. They believe, even after just that one day, that you`re likely a long-term winner. The very best pros have losing days, weeks, sometimes months, so your one day`s worth of losing is utterly irrelevant,
If you happen to be a long-term loser, well, whatever bets you had on Wednesday have frightened the traders, those bets taken in isolation have made you look like a long-term winner. The most common reasons for this are beating SP by too much, too often, and your staking plan, eg; £5 at 16/1 that shortens to 14/1, then £100 at 5/1 that shortens to 5/2. Even if they all lose, the bookie can see you`ll beat him, long term.

If you`re a long term winner, I`m surprised you haven`t come across this before; if you`re a long term loser, just start doing whatever it was you were doing on Wednesday!