Click here for day one results
Click here for more Wimbledon news

Qualifier Ivo Karlovic created one of the biggest Wimbledon upsets of all time to defeat defending champion Lleyton Hewitt on Centre Court on Monday.

The 6ft 10ins Croat - ranked 203 in the world - stormed back from a set behind to secure an incredible 1-6 7-6 6-3 6-4 win over the Australian.

Hewitt is the first defending male champion to lose in the first round since Manuel Santana in 1967.

Only three weeks ago Karlovic had been beaten by Briton Alex Bogdanovic in a Challenger tournament in Surbiton.

But once he found his range with his booming serve and sleek volleys he managed to secure a remarkable win.

A dejected Hewitt said afterwards: "I could have been 6-1 4-0 up and I just didn't take my chances.

"If I got on top of him it makes life a lot tougher for him to come out and keep serving.

"I gave him his chances and to his credit he picked up and his game got a lot better.

"At the end of the day I'd be disappointed losing in the first round at Wimbledon at any time.

"You've got to deal with it - it's hard at the moment trying to say you can learn from it but hopefully I can, see where things went wrong.

Not surprisingly it was fellow Croat Goran Ivanisevic, who lifted the famous gold trophy on the same court two years ago, who was the first to congratulate Karlovic by phone, which prompted something of an understatement.

"Back home this will be a big story," said Karlovic.

"Goran was always my idol and I hold him as a god.

"In the first set I was completely scared but after I saw that I could beat him I began to play better. I saw him (Hewitt) play last week and he didn't play anything special. I was prepared to win. I began to believe I could win in the third set."

Elsewhere on the first day, Greg Rusedski set up a mouth-watering clash with Andy Roddick with a comfortable first round victory over Alexander Waske.

Rusedski defeated Waske 7-6 7-5 7-6 on Court One to make it six wins in a row after his 13th career title in the Samsung Open in Nottingham on Saturday.

The British number two faced just two break points in a match dominated by big serves, perfect preparation for his meeting with Roddick, the man who equalled his world record fastest serve of 149mph two weeks ago.

And Rusedski said afterwards: "You get on a roll and win a tournament and then you feel 'I'm back.'

"It was great to get by the first round in straight sets and the crowd gave me as much support as I could ask for."

"For about nine games I wasn't getting a read on his serve whatsoever, and he was serving the corners really well," added Rusedski who climbed to 51 in the world rankings courtesy of his victory in Nottingham. "That's the way grass court tennis can be.

"I thought I started to play well from about 5-4 in the first set but he played at a very high standard.

"But I'm going to have to improve my level again against Roddick. I'm looking forward to our re-match."

Queen's Club winner Roddick looked in fine form as he swept aside Davide Sanguinetti in his opening match.

The fifth-seeded American beat his Italian opponent in straight sets on Court One.

Roddick's famous serve was working well and he had few problems in winning 6-2 6-3 6-3.

Roddick is clearly in confident mood. Afterwards he said: "If I had to pick six guys to win the tournament I might throw myself in there. After Queen's there is more attention on me now but it's not a total shock - it comes with the territory."

Roddick also expressed his shock at Hewitt's early loss.

He added: "If you play a tall guy like that who is serving out of the trees it is always going to be tough.

"Equally, you are always going to play a couple of bad games because that is the nature of tennis.

"However, Lleyton is normally great at getting through those situations but I guess every once in a while it is going to catch up with you."

Another of the big guns in action on Monday was Roger Federer.

He raced into the second round with an assured display in a straight-sets victory over Korea's Hyung-Taik Lee.

Aside from a minor stumble when he wasted three match points at 5-4 in the third set, Federer was impressive, offering a variety of shots and showed willing to attack the net.

Federer failed to take another two match points when Lee was serving at 6-5, but it was only a matter of time before he wrapped up the win.

He did so in a tie-break, in which Lee's resistance was broken, and Federer wrapped up his 6-3 6-3 7-6 (7-2) win.

One of the lower-ranked Britons, Lee Childs, got the British challenge off to a great start, producing the best win of his career to stun 33rd seed Nikolay Davydenko.

The 21-year-old from Somerset thrilled the packed crowd on court 13 with a 2-6 7-6 (7-2) 1-6 7-6 (7-5) 6-2 victory over the Russian.

Childs successfully bridged a chasm of 452 places in the world rankings to win his first five-setter and reach the second round of a Grand Slam for the first time.

"I was a bit nervous to start with, a bit frozen if you like," he said.

"I was just a bit tight playing at Wimbledon but, after I got going, I felt at home."

The Briton was simply irresistible in the deciding set and thoroughly deserved the lucky net cord on match point.

"After that fourth set, the momentum was with me," he said.

"I felt I was hitting the ball well. I didn't feel too much pressure.

"But it's one match. I've got to try to build on that, get through my next one and just take it a step at a time."

Childs will now play Spain's Rafael Nadal, who gained a surprise win over many people's title outsider Mario Ancic.

Another man tipped as a decent outside bet, Taylor Dent, also made his exit in the opening round. He lost in four sets to another big server from Croatia - Ivan Ljubicic.

There was disappointment for two other Britons, Alan Mackin, who lost 6-2 6-4 6-2 to Flavio Saretta, of Brazil and Arvind Parmar who went down 6-3 6-4 6-1 against eighth seed Sjeng Schalken.

American Vince Spadea earlier became the first seed to fall. He lost in straight sets to Max Mirnyi.

Spadea, seeded 31, was beaten 6-2 6-4 6-4 by Mirnyi.

He was later joined on the sidelines by Argentine claycourter Gaston Gaudio, whose defeat against Nottingham Open runner-up Mardy Fish was no surprise, and 19th seed Fernando Gonzalez of Chile who was beaten 6-3 6-4 7-6(8-6) by Austria's Jurgen Melzer.

Another seed, Paradorn Srichaphan, survived a scare to make progress.

The 12th seed, who famously beat Andre Agassi at last year's event, won the first two sets against Dominik Hrbaty but was forced into a decider before going through.

Ninth seed Rainer Schuettler also went through with a four-set win over Michel Kratochvil.

In the women's singles, there were routine wins for the leading seeds in the bottom half of the draw - Kim Clijsters and Venus Williams.

Clijsters was in no mood to follow in the footsteps of boyfriend Hewitt as she romped to a 6-0 6-0 victory against Paraguay's Rossana Neffa-De Los Rios.

At just 32 minutes, it was one of the tournament's quickest ever matches.

Clijsters was pleased to make such comfortable progress.

"To have a match like this is great. Its always nice to have one of those," she said.

Asked whether she was champion material, Clijsters said: "I'll work as hard as possible. I'll fight as hard as I can and I'll do everything 100% and if it happens, it happens, and if it doesn't I can't blame myself."

Meanwhile, Williams beat little-known Slovakian qualifier Stanislava Hrozenska 6-2 6-2.

Seventh seed Chanda Rubin was another easy winner.

She proved again that she should not be written off as she thrashed Iva Majoli in her opening match.

Rubin, who won the tournament at Eastbourne last week, beat the former French Open champion 6-3 6-0 to make a flying start.

Lindsay Davenport was given more of a workout but still managed to beat Australian Samantha Stosur.

The 1999 champion withdrew during the French Open earlier this month with a toe injury and had been doubtful for Wimbledon.

But she showed she has the fighting spirit required, battling hard for a 7-6 7-5 win.

And ninth seed Daniela Hantuchova overcame the media glare to prevail 6-4 6-1 against France's Marion Bartoli.

Two women's seeds did make an early exit though.

Israeli Anna Pistolesi was beaten 6-4 6-4 by American Samantha Reeves, and Patty Schnyder (20) lost 7-6 6-3 to Hungary's Petra Mandula.

Japan's Ai Sugiyama almost joined the casualty list but instead she fought back to deny Briton Lucie Ahl a famous victory.

Ahl had moved a break up in the final set but the pressure then seemed to get the better of her and she finally succumbed 3-6 6-4 6-4.

British number one Anne Keothavong, who has struggled with a wrist injury in recent weeks, was trailing 6-2 4-0 to Katarina Srebotnik, of Slovakia, when she retired.