Taylor Swift was beaten by Britain's First Lady, Samantha Cameron who topped Vanity Fair's International Best Dressed list 2015.

Britain's Prime Minister David Cameron's wife's look was labelled ''conservative charm'' while the 'Bad Blood' hitmaker came in just behind in second place and was described as ''Prep Power''.

Samantha's most notable outfit was a blue Preen dress, which she wore to meet Britain's Queen Elizabeth at Buckingham Palace earlier this year.

And Taylor's style profile revealed her style icon is 'Breakfast at Tiffany's' actress Audrey Hepburn.

The only other pop stars on the women's list was 'Four Five Seconds' singer Rihanna, who came in at fifth place beaten by George Clooney's Human-rights lawyer wife, Amal Clooney who sat comfortably at fourth behind royalty, Britain's HRH Countess of Wessex.

Meanwhile, a controversial choice was first place for the men's list with 'Love Actually' star Bill Nighy, who said he was inspired by 'Happy' singer Pharrell Williams and 'My Way' legend Frank Sinatra.

Asked who his style icons are, he said: ''Frank Sinatra, David Bowie, Bryan Ferry, and Pharrell Williams.''

The British actor's favourite accessory is a quirky ''polka-dot silk scarf'' designed by Margaret Howell and Pantherella socks.

Asked what his favourite item of 2015 was, he told Vanity Fair: ''Margaret Howell dark-blue-and-cream polka-dot silk scarf. And dark-blue Pantherella socks.''

The British theme continued as Britain's HRH Prince Harry was celebrated further down the list at number eight.

He was crowned ''The Heir With Flair'' and was picked for his style at Royal Ascot races and his choice of a black top hat paired with a blue waistcoat and matching patterned tie.

Vanity Fair's Best Dressed Women:

1. Samantha Cameron

2. Taylor Swift

3. Misty Copeland

4. The Countess of Wessex

5. Amal Clooney

6. Rihanna

7. Charlotte Casiraghi

8. Queen Letizia of Spain

9. Mellody Hobson

10. Francesca Amfitheatrof

Vanity Fair's Best Dressed Men:

1. Bill Nighy

2. Stavros Niarchos III

3. Ike Ude

4. William Ivey Long

5. Jonathan Ive

6. Prince Carl Philip of Sweden

7. Jonathan Tisch

8. Prince Harry

9. Russell Wilson

10. Robert Courturier