Are you going to transfer it to another of your own accounts (would defeat the object) or to someone else? If the latter then it's a gift and they have every right to refuse to ever give it back to you. Also be aware that all large (>£10,000?) money transfers have to be notified by the bank, so there will be a record of it and also if it's discovered that you made the transfer solely to beat the means test eg, for benefits, it will be treated as if it never happened and you will lose the money and the "prize".