Tim Henman launches his bid to reach the Wimbledon semi-final for the fifth time today with the support of two of the game's legends.

But both John McEnroe and Boris Becker warned the British number one not to underestimate unseeded Mario Ancic of Croatia.

Henman and his 20-year-old opponent have never played each other before but 6ft 5ins Ancic, a tennis disciple of Goran Ivanisevic, is recognised as one of the most dangerous floaters in the draw on a surface which suits his big-serving game.

He has the scalp of reigning champion Roger Federer, who he beat in the first round two years ago, to prove it.

''Tim is playing much better when he's not supposed to win easily,'' said Becker.

''He does not have the game to blow away opponents so he has to find a way to win the points but he has proved in the past that he has the ability to beat Federer and Roddick.

''Yes, he has the weapons. His problem is to get to the semi-final without losing too much energy. He always struggles when he is supposed to win easily.''

McEnroe also added his warning, not that it will lower the expectations of a Centre Court crowd who are beginning to believe that this really could be the year when Henman ends the 68-year wait for a British men's singles champion following his thrilling fourth-round triumph against Mark Philippoussis.

''In his first three matches he did not play up to his capabilities,'' said McEnroe, speaking at an event launching the Stanford Financial Champions Tour Rankings.

''I think he did against Philippoussis. It would have been nicer to win it easier but then it would not be Tim Henman. It always seems to be a rollercoaster.

''Henman could be a programmer for the BBC. The ratings must be very good.

''But Ancic is very dangerous. He beat Federer here two years ago.

"I would pick Tim to win but he's got to be ready. Ancic is dangerous.''

He is also fresh, having been required only to play one full set in the fourth round against Belgium's Xavier Malisse, who retired with a back problem.

Henman, who first made the last eight at SW19 back in 1996, is one of the fittest players on tour and in the last six months under the tutelage of new coach Paul Annacone his mental strength has begun to match his physical attributes.

He practised for around 40 minutes yesterday afternoon on Court 10 with Annacone and fitness trainer Johan de Beer and as he signed autographs and chatted with well-wishers his demeanour could not have been more relaxed.

''My game's getting better and better and that's exciting for me,'' said Henman.

''It's been a big last six or seven months and I'm very keen to build on it.

''When I first made the quarters in 96 it was an eye-opener and I was on a sharp learning curve.

''A lot's happened since then. I'm a far better player and I'm now looking to go further.''

If he plays to the level he demonstrated against Philippoussis he should not need the assistance of the patriotic fervour witnessed in his last two matches on Centre Court.

''I've practised with Ancic a bit,'' said Henman. ''He's a good player, knows his way round a grass court well.

"He's been playing well this tournament and beat Federer here a couple of years ago.

''It will have similarities to the Philippoussis match.

"He's a big server, a big guy and likes to get forward so I need to continue to return well and make sure I take good care of my own serve.

''The atmosphere and the level of tension and excitement at the end against Philippoussis was brilliant and that's what sport's about.

''That's why you put in the work and the hard hours on the court and in the gym and when you come through a match like that there is a lot of satisfaction, but there's more to come.''

An entire nation is hoping and praying for much, much more.