Off goes Aaron Morris with that injury and Luke Northmore has to come on earlier than probably planned to rejig Quins' back line.

A big blow for them and Morris who has had an injury-disrupted campaign.

How's your luck Quins fans?

Winger Aaron Morris intercepts the ball in his 22 and then kicks it clear to try and launch a counter and goes down injured in the process!

Another Bristol attacking wave follows and Ben Earl nearly creeps through for a second try only for a knock-on to finally stop the surge.

First quarter flies by in this opening semi-final and it's been all Bristol so far.

Quins unable to get any sort of traction or momentum going.

Hands on the floor of the ruck from Danny Care sees them concede yet another penalty on halfway and Bears kick to the corner again.

Marcus Smith kicks to touch in the Bristol 22 to try and give them some much-needed territory, but Bristol take the quick line-out to clear their lines ASAP.

The relentless early pace continues as Bristol also win the ball from a Quins line-out and a penalty on the floor too.

Quins unable to catch a break at the moment.

Griff: Quins v Bristol has to be the neutrals choice. Rugby romance for either teams to make a final.

Big task here on Harlequins' hands.

They need a bit of composure in the face of this Bristol onslaught.

Pat Lam looks very pleased with what he's seen so far from up in the stands.

Quins in need of the next score you feel to stay in it, but Charles Piutau intercepts on halfway and almosts sprints clear again!

And it's two from two for Callum Sheedy and Bristol...

Really impressive kick from almost back on halfway and it has the legs and a bit more to go over the crossbar and between the sticks.

Really energetic, open start to this match from both sides as they look to run with ball in hand.

Quins turnover on halfway, but Bristol then do the same inside their 22 and then counter down the left with Max Malins and Semi Radradra.

Louis Lynagh though concedes another penalty for Quins with a high tackle on Radradra and Sheedy can take another shot at goal.

First points on the board for the hosts as Bears fly-half Callum Sheedy finds the middle of the posts.

And Bristol win another penalty as Quins flanker Jack Kenningham comes in from the side.

Charles Piutau almost gets away clear out wide but the visitors have some good covering defence.

Bristol though will get an early shot at goal...

Early advantage to Bristol as they win a penalty just inside their half and kick to the corner for a driving line-out....

Here comes the shove.

And we're off!

Wayne Barnes is in charge this afternoon as Bristol kick things off.

Sara Orchard
BBC Sport rugby union commentator at Ashton Gate

Image source, BBC Sport

The atmosphere in the stadium is brilliant, Bristol have had a standing ovation for every warm-up run and coming in and off the pitch.

There is also a corner of a few hundred Quins fans in the stadium who have come with some huge flags and loud voices.

BBC local radio

Both matches this afternoon are live and uninterrupted on BBC local radio and right here on the BBC Sport website and app.

BBC Radio Bristol and BBC Radio London will be in position at Ashton Gate for the first semi-final while BBC Radio Devon will be on hand to describe all the action from Sandy Park later.

Find your commentary of choice by searching through the live coverage options at the top of the page.

Right then - kick-off is just a few minutes away.

Teams will be on their way out on the pitch shortly...

Ben Rogers: Not going to be easy, but I’m feeling good about Bristol’s chances this year.