Gloucester get a lineout close to the line, but a mighty effort from Castres' forwards gets the away pack excited, which winds up the home eight and there is a bit of shoving and shouting after the whistle.

Great stuff from Ben Redshaw, with a fine 50-22 taking advantage of a gap at the far corner.

Seb Blake's first throw in is not straight, although he was risking it to the back in the stiff breeze.

Jeremy Fernandez chips ahead from the Castres scrum, but Gloucester call an easy mark and hoof the ball downfield for territory on halfway.

We're off, Gloucester have elected to run into the wind in the first half.

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Right, there's no time to draw breath - we've got Gloucester v Castres from Kingsholm, where it is blowing a gale.

And of course, Saints get a bonus point themselves. but they trail Pool 4 leaders Bordeaux Begles on points difference.

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And that is the last action of a pulsating match, Pau can count themselves a bit unlucky but Saints were down to 14 for 20 minutes when it was in the balance so that is a fine effort.

Fin Smith stetches the lead - Pau will get nothing despite their excellent effort.

Pau get a bonus point as it stands, but after more chaos Saints have a penalty chance in front of the posts that if taken will take that point for the gap away.

Utter chaos, or classic French rugby, as Pau try to run it out from behind their own line, until it is thrown forward. Saints have a scrum, where they will surely eat up the clock.

Pau do much better at a scrum on their line and kick clear, but Saints have a lineout on halfway.

Henry Pollock punches a hole through, and they move it to George Hendy on the left.

Saints attack and go to the left. Toby Thame gets the ball close to the line, but loses it under pressure.

I'm getting drop goal vibes.

A great run from Clement Laporte sees the winger squeeze down the right flank towards the line. He is stopped by Henry Pollock, then a fight breaks out after the whistle has gone.

It all calms down and Saints have a scrum close to their own line. It's a mess and Saints get a penalty to screams of delight from the Northampton eight.

It is getting a bit chaotic as a Pau attack ends with the ball in touch, but the referee now thinks it was a bad call and the player was not out of play as he flicked the ball back.

Instead, we get a Pau scrum but George Furbank feels the crowd have influenced that decision.

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Toby Thame replaces James Ramm after the 20-minute red expires, Thame is making his Champions Cup debut.

Fin Smith was lining up a penalty kick from inside Pau's half, but the TMO has spotted a knock-on by George Hendy, so Saints won't get the chance to go ahead again.

What a kick!

Desperes nails it from 55 metres out, it's not quite Paul Thorburn territory but it is still a mighty effort.

We're all square again - what a match!

Fraser Dingwall looks like he is away and clear, but the referee blows for a knock-on a few seconds earlier, dragging the centre back.

It's judged to be a deliberate knock-on by Fin Smith, so Pau will go for goal from halfway.