Touch! A superb drop shot from Medvedev sees him consolidate the break with a vital hold of serve.

Wawrinka looks like he'd rather be anywhere else right now. Two more games like that and he will be.

Image source, PA

Aljaz Bedene has a set point in this epic, epic encounter on court three but somehow Ivo Karlovic pulls himself back into it, with a cheeky little lob over his opponent.

This could go on all night...

John McEnroe
Three-time Wimbledon singles champion on BBC TV

There's no question that out of all the top guys, Wawrinka is the most vulnerable. He is in major trouble now. Medvedev is on fire.

Medvedev tries to lob Wawrinka and a lazy waft at it from the Swiss doesn't even reach the net.

Chance for the Russian at 15-30. That's more like it - Wawrinka finishing off a good rally with a fierce smash.

Back comes Medvedev with a deep forehand winner, though. Break point...and he gets it with a passing shot down Wawrinka's right.

Stan on the precipice of a major upset now.

John McEnroe
Three-time Wimbledon singles champion on BBC TV

Mevedev is a natural tennis player. Mentally you can see the brain clicking, he makes a lot of good decisions. The bigger question is, physically how will he hold up? How will his body be in the next couple of years?

Wawrinka isn't troubling the Medvedev serve much at all here.

The Russian looks increasingly comfortable, reeling off these service games and putting all the pressure back on Wawrinka's own serve.

Anyone for a fourth tie-break on court three? This is getting silly now.

Image source, AFP

Solid game from Wawrinka, just what he needed at this point.

He's getting nothing from the crowd and is going to have to raise the tempo by himself.

Medvedev gives him a hand too here, firing long to hand Stan the game.

Three hours and 23 minutes later, and we still don't have a break of serve in this match.

Karlovic has had seven chances, Bedene has had four. But no-one is giving in. Pure stubbornness.

For the second time, the British number four is serving to stay in the match.

Medvedev starts off the fourth set in imperious fashion, banging down an ace and taking control of the game.

Wawrinka fights back to take it to deuce but the Russian regains his composure to force a couple of errors. Over to you, Stan.

Heather Watson needed four match points but she is through to the second round. Watch her winning moment below.

We're approaching the three-and-a-half hour mark on court three, and Ivo Karlovic has fought off two break points to lead again in the fourth set.

Britain's Aljaz Bedene is about to serve to stay in this match.

You can watch live coverage here.

John McEnroe
Three-time Wimbledon singles champion on BBC TV

Stan's mojo is not the same as it is on the other courts. He hasn't been able to rally the crowd behind him, there's not a lot of energy and he has got himself in some big trouble now.

Image source, Reuters

Wawrinka looks in control of this vital game at 40-15 in front but a wonderful improvised return from Medvedev has Stan wobbling.

It's back to deuce, then advantage Medvedev before Warwinka belts a backhand well wide.

The 21-year-old Russian is two sets to one up against the fifth seed on Centre Court.

Daniil Medvedev is still causing Stan Wawrinka no end of problems. The Swiss levels at 4-4 but a blink-and-you'll-miss-it service game from the Russian sees him now just one game off the third set.

The 21-year-old will have to break the fifth seed here, though.

A grimacing Wawrinka still icing that knee at every opportunity. A big game to come.

Ivo Karlovic has had seven chances to break Aljaz Bedene in this match. He's not been able to take any of them.

We go on.

Naomi Broady joins Cameron Norrie and Laura Robson in exiting Wimbledon in the first round this year.

The 27-year-old from Stockport has lost 6-4 6-2 Irina-Camelia Begu from Romania.

David Mercer
BBC Sport commentator

Watson is through and we all say phew. Now she can smile, a smile of victory but most of all of sheer relief.

Point of the tournament (so far) contender from this pair out on Centre Court.

A crocked Wawrinka defies his knee injury to pull off a series of deft volleys, only for Medvedev to match him all the way.

Wawrinka finally has a chance to finish but Medvedev stands tall to block a smash back over the net.

The Russian rather spoils it by handing the initiative in the game back to Wawrinka, who then levels at 3-3 in the third set with a mighty forehand winner.