Justin Theroux asked Jennifer Aniston to marry him on a romantic dinner date to celebrate his birthday at a New York City restaurant.

The surprise proposal - which took place just over a year after they started dating - occurred when the couple were dining at Greenwich Village restaurant Blue Hill on Friday (10.08.12).

Other diners said the pair were openly celebrating at the eatery but a representative for the restaurant would only tell the New York Post's Page Six: ''We are thrilled about the news of their engagement, but we cannot comment on any guests.''

The couple then enjoyed a weekend of private celebrations before Justin's rep announced the news in a gushing statement on Sunday (12.08.12).

His publicist said ''Justin Theroux had an amazing birthday on Friday, receiving an extraordinary gift when his girlfriend, Jennifer Aniston, accepted his proposal of marriage.''

Meanwhile Jennifer, 43, is ''overwhelmed'' by her eight carat diamond engagement ring.

A source said: ''It's a huge emerald-cut diamond. It's a rectangle with tapered diamond baguettes on the sides. It's beautiful.

''Just after Jen got engaged, she called all her friends and told them about it. She was so happy and said she loves The Ring. I think she was overwhelmed and overjoyed by the size and beauty of it!''

The couple have been friends for years but only started dating after filming the movie 'Wanderlust' together.