Image source, Getty Images

Naturally, both sides are concerned for the welfare of the 28-year-old as he leaves the field on a stretcher.

The fans in the stands give him a warm and respectful round of applause and we hope that it is not too serious.

Alofa Alofa arrives onto the park and will move into the role of inside-centre.

James Law
BBC Sport at Twickenham Stoop

There was a collective wince in the crowd as a replay of that hit on Paul Lasike was shown on the big screen.

It was certainly full-bloodied from both players, with the Quins full-back coming off worse.

The medics are taking no chances. The hosts are warming up during the break in play, while Sarries opt for a pep talk.

Referee Luke Pearce stops game is immediately after Paul Lasike gets his technique wrong in a tackle on Will Skelton and he stays down.

The medics are onto the pitch extremely quickly indeed and the Harlequin is receiving excellent care.

Image source, Getty Images

The 19-year-old's kick is straight and true.

The penalty was a result of Danny Care's pass into a retreating Alex Lozowski, that's what rattled the visitors.

We mentioned before kick-off that there's no love lost between these two sides and there's a pause in play as Luke Pearce just establishes a bit of order.

Marcus Smith will line-up his first kick at goal after.

Both sides are just feeling their way into this one and the two scrum-halves are getting to grips with the wind conditions.

The wind is firmly in Saracens' faces and Ben Spencer is struggling to gain any distance on his connections.

In contrast, Danny Care's are flying miles and the latest lands into the hands of Alex Goode.

As well as being televised in the United States and China, this game tonight is also available tonight with us on the BBC via our live text and radio services.

You can listen to the game on BBC Radio 5 live sports extra or by clicking on the links above to listen to their simulcast with BBC Radio London.

Ben Spencer gets two early box-kicks away and the second is secured well by Mike Brown.

Brown shows the type of aerial skills that he's famed for and duly is handed a massive cheer from the home fans.

It's been raining in London since breakfast, not ideal for either side, but they'll just have to park the conditions and make the best of them.

Marcus Smith is the man to get the show on the road... here's to an excellent 80 minutes!

Shortly, Mike Brown and Danny Care will both walk out onto the park with their young sons to mark their respective 300th and 250th appearances for Harlequins.

With a won two, lost three record this season the home side will go into this one as underdogs.

Saracens' form has been strong and the concerning thing for Harlequins will be that their visitors feel that they haven't put together a complete 80 yet.

London derbies are always tasty affairs and we should be in for another good'un.

Image source, PA

With five minutes to go before kick-off, here's a spot of admin for you.

Tonight's referee will be Luke Pearce, he's taking charge of his 80th Premiership game, and alongside him will be Hamish Smales & Robert Warburton. Our TMO is David Rose.

James Law
BBC Sport at Twickenham Stoop

He’s on the cover of the programme and on the back of fans’ shirts - Harlequins have even used milestone man Mike Brown’s name to form part of tonight’s media WiFi code!

In case you don’t already know, the England full-back is making his 300th appearance for the club.

The kick-off time has raised eyebrows but it’s allowed people to walk straight from the Northampton-Leicester game across the road. Also, the match is the first-ever club rugby match to be televised live in America. Intriguing.

Let's open the form book and see what it tells us...

Harlequins have won just twice at The Stoop in Premiership Rugby since December, against Bath in March and Sale in September.

On the flip side, Saracens have now won 12 successive Premiership matches, the last 11 (including last season’s play-offs) scoring four or more tries in each.

Mark McCall's outfit have not been defeated since Leinster knocked them out of the European Champions Cup at the quarter-final stage in Dublin in April.

Image source, Rex Features

It's a night for milestones and here's another with Maro Itoje set to reach 100 appearances for the North London outfit off the bench today.

An impressive feat given his tender years...

Image source, Getty Images

"He is going to end up being the most-capped Harlequin of all time, of that I have got no doubt. To have played 300 games for his club and over 70 for his country is an incredible achievement. With his bravery, courage, tenacity and how he plays the game, he gives the team confidence."

Paul Gustard’s words about full-back Mike Brown, who came through Harlequins academy and scored a try against Doncaster Knights when he made his first-team debut in a Championship match.

Image source, Rex Features

Mark McCall has decided to make six changes to his XV for today’s London derby.

Brad Barritt misses out after having an operation on a facial injury that he picked up against Bath so Nick Tompkins comes in at 13 and Alex Lozowski moves to inside centre.

Alex Lewington and David Strettle grab starts on the wings and Ben Spencer takes the scrum-half jersey. Will Skelton is promoted to starting lock and Mike Rhodes takes the open-side slot.

From the bench, Maro Itoje is ready to make his 100th Saracens appearance.

Image source, BBC Sport

In this evening’s encounter Mike Brown will make his 300th appearance for Harlequins at the Twickenham Stoop while scrum-half Danny Care will be running out for his 250th club appearance.

US international Paul Lasike is a new face at inside centre. He’s a former NFL fullback with the Chicago Bears and replaces a rested Ben Tapuai.

Hello again!

Welcome back to part two of the Premiership day, tonight's evening session is all about Harlequins taking on Saracens at the Twickenham Stoop.

Kick-off is on the way in 15 minutes so we've got ample time to recap on all of the afternoon's action and focus on the two protagonists.

So, you've just got time to grab a bite to eat and a brew before we'll be back with you at 7.15pm. There's plenty more to look forward to and a lot of talking points to discuss before the final match of the day. Until then...

Don't forget that a little later on we'll be bringing you all of the action from the second derby match of the day as Harlequins host Saracens.

The encounters between these two sides are always feisty ones.

The last seven meetings between the two clubs in this competition have all been won by the ‘home’ side on the day but Saracens have now won twelve successive Premiership matches! A big task for Paul Gustard's outfit at The Stoop then.