Steve Smith has somehow gone up another level while batting his team into Ashes ascendancy yet again, notching his third double century against England to help Australia reach 497 in the first innings of the fourth Test at Old Trafford.

Australia has a 474-run lead after England spent the final part of the day at the crease, heading into day three on 1-23 after Smith demoralised the hosts for a second straight day.

Smith's 211 made him the highest run scorer for the series despite missing the second innings of the second Test and all of the third, and the highest Test run scorer of 2019 despite not playing a Test for the first seven months of the year.

It was also the third time in the past three Ashes series that he has passed 200 and he took his average across those series to just over 99.

"Obviously, it was disappointing to miss the third Test at Headingley, particularly with the way it finished up, it was an amazing Test match and a shame not to be a part of it," Smith said.

"It gave me time to recover and get my head right after my concussion. I felt good coming in to the game and was confident and fortunately I scored some runs and got ourselves in a nice position with 497 in the bank."

"Lord's was a tough wicket," Smith said of the only pitch he has not scored a century on this series.

"It was up and down and with the slope, his angle wasn't very easy with the wicket being up-and-down. That was hard work.

"I said before the game that if they bowl a lot at my head then they're not bowling at my stumps and trying to get me out LBW and caught behind the wicket.

"And I think that perhaps played into our favour a little bit in this innings."

Denly removed to close brilliant day for tourists

After Smith's heroics, captain Tim Paine, having scored a half-century earlier in the day, declared on 8-497 to gave England just over half an hour to bat.

Mitchell Starc and Josh Hazlewood opened the bowling, but first change Pat Cummins capitalised by taking the wicket of Joe Denly, thanks to a sharp catch from Matthew Wade at short leg.

Steve Smith took on the short ball early on day two. ( AP: Rui Vieira )

The day had started with such promise for England when Travis Head added just one run to his overnight score of 18 before being trapped LBW by Stuart Broad in the fifth over.

"I think we saw when Stuart Broad came on with the new ball, he bowled some really nice lengths and beat my bat on the outside a couple of times and I got an inside-edge to fine-leg," Smith said.

"He was quite challenging when he hit that length. For them to go as short as they did and as early as they did with the new-ball, softened that ball up and played into our hands."

Smith continued on his merry way alongside Matthew Wade, and had just made it to 90 when his batting partner played a rash shot to the spin of Jack Leach and holed out to mid-on for 16.

That brought captain Paine to the crease after a week of talk about everything from his batting to his tactical nous to his right to be in the Test team, and he went about correcting the record on the former.

The first order was staying in to see Smith to his century, which he did as England's bowlers regularly allowed the in-form Aussie to nudge singles all the way through the not-so-nervous 90s and reach triple figures for the third time in the series.

The pair made it to lunch, but England had more to chew on after the break, when Paine, on 9, chased the fourth ball of the afternoon session and edged Broad straight to second slip, only for Jason Roy to grass a simple chance.

On a day when chances were rare, Stuart Broad watched Tim Paine dropped at slip. ( AP: Rui Vieira )

If that was frustrating, things got maddening for the English in the 75th over when spinner Jack Leach found Smith's outside edge and Ben Stokes took the catch at slip, firing the ball into the ground in a show of relief with the batsman on 118.

But the celebrations were short-lived as slow-motion replays revealed Leach had bowled a front-foot no ball by a slim margin, allowing Smith to be recalled and carry on punishing England.

Paine finds form with much-needed 50

Paine got in on the act and made his way to 49 when, halfway through an 18-ball stay on the score, he smacked a relatively simple catching chance to mid-on and substitute fielder Sam Curran — called onto the field after Ben Stokes went off with shoulder soreness — gave Paine another life against an exasperated and tiring attack.

The skipper eventually cashed in and passed 50 for the first time since a match-saving dig against Pakistan last October.

The current captain and the man he replaced spent 40 overs together out in the middle. ( AP: Rui Vieira )

He made it to tea but only lasted one ball in the final session, nicking off to Craig Overton before a good portion of the crowd had resumed their seats.

Pat Cummins came and went, adding only 4, and then the fireworks came as Smith and Mitchell Starc, who at one point hit four successive boundaries off Broad, freed the arms.

Once again, Smith only got out when he was slapping quick runs, reverse sweeping Joe Root to backward point to fall for the third-highest score of his career.

With much of the build-up to the fourth Test centred on Jofra Archer's battle with Smith, it was the Australian who undoubtedly took the honours, with the paceman struggling to figures of 0-97.

See how the day unfolded in our live blog.