120 laps to go. Dane Lasse Hansen, in third place, has made a break for it, trying to make up a lap on the rest of the field. He wins the next sprint, with Cavendish in second. The Briton is still second overall.

Sir Chris Hoy
Six-time Olympic cycling champion on BBC One

It's a good start for Mark but I think Viviani is looking ominous. He has the answer in terms of top speed. But one lap gained and it could all be very different.

I'll be honest, this is a pretty ridiculous spectacle. The 18 riders are doing lap after lap, not unlike a cycling version of It's A Knockout. If you didn't know how this worked, you'd have no chance of picking it up as you go along. It's also enough to make you quite dizzy.

Chris Boardman
Olympic cycling champion on BBC One

That's what you have to do - lose some battles in order to win the war. Cavendish can't do much chasing now, that cost him quite some energy.

That's a blow to Cavendish. Leading down the straight, he was pipped by Viviani on the line. On point gained earlier, two points lost here.

Cavendish, by the way, picked up a point on Viviani in the first sprint. Here's the bell for the second sprint...

Anna Thompson
BBC Sport in Rio

Laura Trott is one popular lady in the velodrome as the loud cheers fill the venue and British fans fly their flags and chant her name as she goes into the lead in the women's omnium after two events.

Now it's the moment of truth for Mark Cavendish. Can he win a first Olympic medal?

Simon Brotherton
BBC commentator in Rio on BBC One

Mark Cavendish came to Rio not as the favourite for the gold medal. He comes into this final race not the favourite. Is it possible? Does he have the ability to win? Yes, he does.

Sir Chris Hoy
Six-time Olympic cycling champion on BBC One

This is a huge, huge task for Mark Cavendish. Elia Viviani is in great form and has a lead. It is very exciting and I'm getting nervous.

Mark Cavendish, in second, is 16 points behind leader Elia Viviani, so a gold medal is possible.

Seventh-placed Fernando Gaviria has launched an early attack, winning the first sprint. Just the 150 laps to go...

If you're confused at any point over the next 40km, you probably won't be alone.

The points race is designed to be a grand finale of the omnium, with huge rewards on offer.

The riders will do 160 (that's not a typo) laps of the track, with sprints every 10 laps. Points on offer for each of those, with 20 also on offer if you manage to lap the field.

Ben Dunbar: Laura Trott absolutely smashed that. I think if it had been 4000m and not 3000m she would have lapped a world champion twice.

Guy Hornsby: Blimey @LauraTrott31 really is a fearsome athlete. The definitive all-round track cyclist. Sensationa

Louis Bounds: Mark Cavendish now is your time. Go get your medal and do us proud. You deserve it

Stephan Shemilt back with you for a little while, refueled and ready for the final event of the men's omnium.

Fuel very much needed - this one is 40km.

Chris Boardman
Olympic cycling champion on BBC TV

Laura Trott has beaten the former world champion. Quite a remarkable ride. She had a beautiful line on the track.

Ben Dunbar: Laura Trott absolutely smashed that. I think if it had been 4000m and not 3000m she would have lapped a world champion twice.

Carrie Gregory: Was I imagining that, or was Laura Trott grinning for the last couple of laps?

Laura Trott has a six-point lead over the field after two events.

Superb. 

Wow! Laura Trott clocks 3:25.054 to win the individual pursuit! She beat Tatsiana Sharakova by 12 seconds, but also beats Sarah Hammer by over a second.

Stunning display.

Laura Trott still powering on...

Laura Trott eating up the track. She clocked 3:30.547 in London, she's going to smash that. She is almost on the wheel of Tatsiana Sharakova already. She's past her with 1,000m to go!

Chris Boardman
Olympic cycling champion on BBC TV

Laura Trott is going to have to produce a personal best here, but that is how it should be at the Olympics.