Trenchcoats and cardigans up the fashion stakes at Wimbledon (Reuters)

LONDON (Reuters) - On a gloriously sunny afternoon at Wimbledon, Serena Williams strode onto court in a trenchcoat.

With the sun beating down on Centre Court, defending champion Roger Federer appeared in a cardigan. All that was missing was his pipe and slippers.

"Game, Set and Mac, Miss Williams," the Daily Express decided on Tuesday after the 26-year-old former champion grabbed all the headlines with the most eye-catching outfit on day one.

Williams made a stuttering start before overcoming Estonias Kaia Kanepi -- but reporters afterwards were more interested in her outfit than her tennis.

Was it a Sixties retro look? Can you tell us about the fabric? Is it lightweight or porous? No question was too trivial.

Federer, seeking his sixth Wimbledon title in a row, swapped his white blazer for a Great Gatsby-style cardigan which also had reporters seeking fashion tips.

It felt more like a day on the catwalk than the opening of the worlds most famous tennis tournament -- but fashion has always been an integral part of Wimbledon with its strictly enforced "predominantly white" dress code for players.

After last years rain-soaked Wimbledon, spectators blinked in amazement at the sunny start to the 2008 tournament and Serena Williams joked about her outfit "I dont think its going to keep the rain away but we can always hope."

"I absolutely love trench coats. I live in Florida. I probably have more coats than anybody," she said.

But she admitted "It doesnt really add up" to live in the sunshine state and have that many coats.

Waxing lyrical about her warm-up attire, she said "its ladylike and Im very ladylike. It goes perfect with my personality and everything else. Its perfect for me."

Donning a cardigan can be a cutting edge fashion statement -- Soccer player and style icon David Beckham has started wearing them -- but, as The Independent newspaper warned on Tuesday "Theres a fine line between cool cat and old codger."

Federer extended his unbeaten run on grass to 60 matches when easing into the second round with a straight sets demolition of Slovakias Dominik Hrbaty.

After much discussion at his post-match press conference about his tennis form, it was onto the cardigan.

Federer, it appears, was thrilled to put aside the white blazer he had won for the last two years.

"I thought two jackets was enough. Lets move onto something a little bit different," he said.

"We thought about something nice like a cardigan, a jumper. I think the result is nice as well. I have a belt as well this year. Just some new fresh things. Its a little bit more easier to wear than the jacket to be honest."

(Reporting by Paul Majendie, Editing by Justin Palmer)