One of Oxford's newest tourist attractions has reported a dramatic rise in visitors, with bookings booming in the past three months.

Oxford Castle Unlocked, which offers people a guided tour of the 11th Century castle and prison complex, has taken 13,000 bookings in the four months since February - more than three times the 4,000 tours booked in the whole of last year.

The increase has been accompanied by a similar rise in overall visitor numbers, up from about 50,000 in total last year to 25,000 in the first third of this year.

Managers of the attraction, which opened in June 2006, believe marketing and word-of-mouth recommendations have led to the surge in interest.

Visitor centre manager Emily Hirons, pictured front with, from left, tour guide Tracy Slator, Andrew Worman and Helen de May, said: "We always knew we'd grow in popularity as an attraction - but even we didn't expect to take off this well and be so successful so soon."