Hello and welcome to live coverage of the big one - the final day in the mountains and Geraint Thomas' day with destiny - the 200.5km Pyrenean stage 19 from Lourdes to Lauruns.

It's Katusha-Alpecin and the mouthy figure of Nils Politt who have come to the front of the pack now to help Sky with the pace-setting. Ilnur Zakarin's team missed all the moves and don't have a rider in the mix - and they'll also be hoping the Russian can rise into the top 10 today. He's currently 12th place on GC.

Puncture for the Luxembourg champion Bob Jungels who stops for a bike change and a new bidon before getting on his way. He'll be riding between the two leading groups now - and may precipitate the coming together of these forces.

Damien Gaudin leads the leading group of six riders over the summit with a gap of 1:05 over the 12 chasers and almost five minutes over the pack.

Peter Sagan has come alongside the Sky train on the front of the peloton and is chewing the fat with Luke Rowe. He's covered in bandages following his crash in stage 17 and it's not clear what he's point he's raising. He was distanced on the first climb and so may simply be asking the team-mates of the yellow jersey to go easy on him.

We're onto the Cat.2 Cote de Capvern-les-Bains (3.4km at 5.1%) and the two chasing six-man groups have come together to make a 12-man chase group, 1:05 down on the leading sextet. The peloton has called a ceasefire with the gap now almost four minutes.

There's a third six-man group now on the road involving Bauke Mollema, Mikel Nieve, Tom Jelte Slagter, Marcus Burghardt, Daniele Bennati and Romain Hardy. So we have a 6-6-6 situation ahead of the second of these early Cat.4 climbs.

Here's a nice photo from the start of the white jersey (Pierre Latour), the yellow jersey (Geraint Thomas) and the polka dot jersey (Julian Alaphilippe). I can only imagine that the green jersey (Peter Sagan) was pulling a wheelie somewhere off-camera.

Alaphilippe and Chavanel make it over so we now have six chasing six.

Just to remind you, Alaphilippe leads the polka dot standings with 140 points to Barguil's 73 points. It's a huge buffer going into the final mountain stage, but there are 82 points (81 now) up for grabs today, and so not a mathematical impossibility for the defending polka dot champion to leapfrog his compatriot today.

The two trios have come together to make a leading sextet - but behind there's an explosion of movement with the peloton split into two large groups and another cluster of four riders (including Warren Barguil) trying to bridge over, sparking a response by the polka dot jersey of Julian Alaphilippe, who has countered with Sylvain Chavanel.

Adam Yates (Mitchelton-Scott), Bob Jungels (QuickStep Floors) and Tanel Kangert (Astana) have zipped clear in a bid to bridge over to the leaders. They would be solid reinforcements for that initial move - but things are still very active behind.

The gap is up to 50 seconds for the three leaders but behind the peloton is strung out as numerous riders try to force a counter attack.

Peter Sagan, the green jersey, is already in trouble. The Slovakian was slipping off the back of the pack over the summit of that climb following his crash a couple of days ago. He will need to finish within the time limit to be assured of a record-equalling sixth green jersey in Paris.

It's Dillier who takes the solitary KOM point over the summit of the Cat.4 Cote de Loucroup (1.8km at 7.2%) with much movement behind from the peloton.

Three riders - Damien Gaudin (Direct Energie), Lukas Pöstlberger (Bora) and Silvan Dillier (AG2R) - break away on the start of the first (and smallest) of six climbs.

They're off! The remaining 146 riders get this decisive stage under way and there's a flurry of activity from the outset.

The final day in the Pyrenees includes the legendary trident of the Col d’Aspin, Col du Tourmalet and Col d’Aubisque after a start in Lourdes (where many riders will be hoping for a miracle and/or divine intervention). A fast downhill final 20km to the finish will keep hearts-in-mouth all the way to Laruns.

Yesterday, Frenchman Arnaud Demare put his Herculean Pyrenean struggles behind him with victory in Stage 18 of the Tour at Pau ahead of compatriot Christophe Laporte as Team Sky’s Thomas retained the yellow jersey ahead of a final day of reckoning in the mountains. Read all about the first stage win in this year's race for a French team below...