The 'Choice' host and the 41-year-old TV presenter have sparked engagement rumours after the blonde beauty was spotted wearing a wedding ring on her left hand.
The pair are said to have hosted an engagement party for friends and family on Sunday (29.07.12) at London's The Goring Hotel, where Cat, 35, is thought to have showed off her diamond ring.
A source told the Daily Mirror newspaper: ''Cat and Patrick have been friends for years, so even though they've only been dating a few months, they know they've found The One in each other.
''They wanted all their friends to know they were engaged straight away.''
In May, Patrick moved into Cat's £1.7 million Californian home and earlier this year Cat admitted she loves it when fans give the couple dual nicknames.
She said: ''People call us Pat-Cat or Catric. And there is another one which my friends have come up with which is called Caddy, because he is called Paddy.''