You don't say how much you put on this horse. As the others say, you will get back 2.5 times your stake as winnings, and you'll get your stake back. But there is tax to take out isn't there?
There is no betting-tax any more. I assumed that the figure 10 was a reference to a stake of that amount rather than the horse's number, so �35.00 as already stated.
Thanks beejay- last time I put a bet on was nearly 40 years ago so things must have changed- in those days you either had tax deducted from winnings or you could be taxed at source on your stake instead if you wanted.