One Direction have congratulated Britain's Duchess of Cambridge on her second pregnancy.

The 'Steal My Girl' hitmakers - made up of Harry Styles, Louis Tomlinson, Zayn Malik, Niall Horan and Liam Payne - greeted the brunette beauty at the Royal Variety performance in London last night (13.11.14) and offered their kind words the mother to be.

Harry, 20, admitted he was surprised Duchess Catherine - who already has a 15-month-old son George, with her husband Prince William - ''didn't look bumpy'' at 16 weeks pregnant.

He is quoted by the Daily Mirror newspaper as saying: ''I said congratulations on the bump. (Though) she didn't look bumpy.''

While the group chatted with the couple about their upcoming tour plans, Louis, 22, feared he may have offended the duchess when he failed to follow the proper etiquette expected when addressing a member of the royal family.

He said: ''I didn't say ma'am. I said - Hi. How are you? I'm Louis.''

Liam feared his band mate may have made a lasting impression on the couple for the wrong reasons.

He said: ''So he's off to a bad start.''

The 21-year-old singer also confessed the meet and greet was one of the most nerve-wracking moments of his life.

He said: ''It's the most nervous I think I've ever been in my life.''

The band and the royal couple were joined at the event at the London Palladium by a host of other stars including singers Ellie Goulding, Ed Sheeran, Demi Lovato and music mogul Simon Cowell.