Free caller display for a year if you renew your phone contract for a year. Handy if you have just signed up for one of the recent broadband deals.
Blurb from BT below.
It can be handy to know who's calling you before you decide to pick up the phone. Whether it's a number you don't recognise or you're busy with something more important, Caller Display shows you the number of the person calling, so you can decide whether to pick up or leave it to your answering service.
BT Privacy with Caller Display costs just £1.75 a month. Customers can get the service free for 12 months when taking out a new 12 month line rental contract.