The Irish hunk was filming a scene for his latest movie
'London Boulevard' in the UK capital last week when a female admirer snuck past several burly security men and bounded into the backseat next to him.
A source said: "This woman came from nowhere and tried to jump in the car while they were shooting a scene. Colin went crazy and started screaming like someone had shot him. He was shouting at the girl to keep away. It really freaked him out."
However, the 33-year-old star can't have been too traumatised by the event as he joined cast and crew celebrating the end of shooting on Friday (14.08.09) with a luxurious meal at exclusive bar and restaurant The Lonsdale in London's Notting Hill district.
The film - which also stars British beauties Keira Knightley and Anna Friel - is due for release next year and will see the womanising actor portray an ex-convict trying to win the heart of a reclusive actress, played by Anna.