William Hill run this cyclically but it results in an easy £25 profit when you take advantage of it. I've done the deal myself and can confirm that it has tracked.
TCB lists the deal as £50 but it tracks at £60. I lost my £35 but you could always double up! Just be sure not to deposit any extra money.
This deal ends today, so do be quick!http://www.topcashback.co.uk/william-hill-casino/