If you think Harry will get down on one knee in 2013 you can get odds of 3/1.
The couple were recently photographed attending a James Blunt concert and a night out in London's West End watching hit musical The Book Of Mormon.
The prince, who is fourth in line to the throne, has been with Cressida for over a year following a long-term romance with previous partner Chelsy Davy.
Cressida, who is very shy and does her best to avoid the spotlight, were reportedly introduced by Harry's cousin Princess Eugenie and grew close soon afterwards.