Brian Lara's 400*, made against England in 2004, is the highest individual score in Test history.

Only five men have ever scored 300 for England in a Test. That is Root's first target.

The last Test total of 700 or more was made by Sri Lanka last year. It isn't that rare. There have been 25 instances in total with these five being the highest scores of all time:

952-6 dec Sri Lanka v India, Colombo, 1997

903-7 England v Australia, The Oval, 1938

849 England v West Indies, Jamaica, 1930

790-3dec West Indies v Pakistan, Jamaica, 1958

765-6 dec Pakistan v Sri Lanka, Karachi, 2009

Image source, Getty Images

903-7 v Australia, The Oval, 1938

849 v West Indies, Jamaica, 1930

710-7 dec v India, Edgbaston, 2011

658-8 dec v Australia, Trent Bridge, 1938

658-3 v Pakistan, Multan, 2024

657 v Pakistan, Rawalpindi, 2022

I'm glad you asked, Chris.

Firstly, and according to analysts CricViz, this pitch was rated as the fifth-flattest since such stats started being taken at the start of 2007. That has meant it has been a dream for batting.

Having got to this position, England clearly think piling on more and more runs, declaring and then bowling Pakistan out before their two combined innings scores better England's is their best way to win.

They will hope the pressure of the second innings combined with any amount the pitch does deteriorate will give them a chance.

Pakistan will just bat and bat again and try and save a draw.

Image source, Getty Images

Joe Root and Harry Brook have just batted on and on and on for England. It's basically just been a matter of counting the records they tick off.

From 492-3 overnight England have progressed to 658-3. They now lead by 102.

Root, who was dropped this morning on 186, now has his highest Test score. Brook does too. It's the first time he has scored 200 in a Test.

The Yorkshire pair are now closing on England's all-time highest partnership in Tests.

The record is held by Colin Cowdrey and Peter May, who put on 411 against West Indies in 1957 and Brook and Root's partnership is worth 408.

This is now England's joint-fourth highest team total in Tests.

Thanks Sam and good morning all. I've spent more time looking up stats this morning than I'd like to admit.

With so many records being broken or on the cusp of being broken, it's time for us to make a change.

Here to take you through all the key facts and figures - and then the afternoon session - is our resident would-be statto Matthew Henry.

Jonathan Agnew
BBC cricket correspondent

It's an outstanding session for England there again. Clearly, there's full of admiration for Joe Root who's walking off and heading for the dressing room again.

Steven Finn
Former England fast bowler on BBC Test Match Special

The reason why Joe Root's such a run-scoring monster is that his appetite is never satisfied. He just wants to score as many runs as he possibly can.

Pakistan are on the ropes and they are taking the body blows. England will land the haymaker later on, but for now, they are just dipping their bread and having some fun.

That's lunch and it's another wicketless session.

It's been a batting masterclass from Joe Root and Harry Brook. Conditions could hardly be more favourable but this is how you take full advantage.

They've taken England to their joint-fourth highest total in Tests and are set to sail past that after lunch.

The 409-run partnership is also just two off the England Test record.

It was mentioned to me a little earlier that this had become like a net session for Joe Root and Harry Brook.

I'd wager they've both had far more challenging net sessions on surfaces that are rather less flat.

Image source, Getty Images

If you are wondering there's still a very long way to go in terms of the highest partnership for any team in a Test.

Kumar Sangakkara and Mahela Jayawardene put on 624 for Sri Lanka against South Africa in 2006.

Prior to this there have been 15 stands of 400 or more in Tests.

Ramiz Raja
Former Pakistan captain on Test Match Special on BBC Sounds

Both batters have now completely switched on for the white-ball mode.

It's just too easy for Harry Brook right now.

Width from Naseem Shah and Brook just helps the ball up and over the slip region to the boundary to bring up the 400 partnership!

Absolutely remarkable. That is now England's second highest stand in Test cricket and they're just a few runs off the record...

Andy Zaltzman
Statistician on Test Match Special

This is now Joe Root's highest Test score, overtaking the 254 he made against Pakistan at Old Trafford in 2016.

It's the 20th time a team have had two double centurions in the same innings and only the second time for England - the other one was when Mike Gatting and Graeme Fowler picked up double hundreds in Chennai in the 1984-85 series against India.

Stephan Shemilt
BBC Sport chief cricket writer in Multan

Image source, Getty Images

Never have two batters got triple hundreds in the same Test innings. Just saying.

Top shot!

Harry Brook gives himself a bit of room and thumps Saim Ayub over extra cover off the back foot for four.

The lead is approaching 100 now, it will grow far larger than that before England are finished.

Meanwhile, Joe Root has now moved to his highest score in Tests.

Joe Root is something very special. But it is probably fair to say the thing testing him most at the moment is exhaustion rather than the bowling.

He's been exceptional, though, especially given we're less than 10 minutes from lunch on day four and he's been off the field for a grand total of eight balls in this match.