Image source, Getty Images

So Steve Smith ends unbeaten on 102, with Mitchell Marsh 29 not out.

England did get two wickets today - David Warner looked on course for a second ton in the match but skied Joe Root to James Vince at cover for 86.

And Stuart Broad then produced a rare delivery that did a bit off the seam, with Shaun Marsh nicking behind for four to give England hope as they went into lunch. ]

But this pair just shut it all down after that.

Geoffrey Boycott
Ex-England batsman on BBC Test Match Special

Congratulations to Steve Smith. He gets on the back foot and it is difficult on these flat pitches to get him out of the comfort zone.

Handshakes all round as Steve Smith and Mitchell Marsh depart the field, followed by England.

A quick word on Marsh - he looked like he'd nick off at any time during his first 20 balls faced but then looked like he could've batted for five days straight thereafter. That's a stoic innings in support of his captain to save the Test.

England are back out, crossing the field to applaud their travelling support.

Image source, Getty Images

How very pointless. Moeen Ali bowls another dot ball and Australia do then declare.

Joe Root and Steve Smith shake hands and agree to the draw.

Australia lead the five-match series 3-0 after the fourth Test.

The umpires have asked Australia if they would like to declare now as that would give the captains the option to shake hands on the draw.

"Nah, we'll chase them down," chirps Jonny Bairstow from behind the stumps.

At least he's kept his sense of humour out there.

Andrew Samson
BBC Test Match Special statistician

They were the first extras of the innings. We were on course for the second-highest total without any extras in Test history.

That was the only excitement left in the game for me.

Root slides one down and Smith tries to flick it fine, misses with the bat but it runs away for four byes.

Brief lbw appeal as Root gets it through Smith's defends but that pitched miles outside leg and probably wasn't hitting anyway.

Joe Root is bringing himself back on. It's the England captain's 27th birthday today.

It's safe to say his day very much peaked when he got David Warner out.

The rest? Not so happy.

Geoffrey Boycott
Ex-England batsman on BBC Test Match Special

I feel sorry for Alastair Cook. You like to make hundreds when you win the game or save the game.

Moeen to Marsh. Six dot balls.

I haven't quite lost the ability to type, it's just there really isn't much to say about what's going on out there.

Geoffrey Boycott
Ex-England batsman on BBC Test Match Special

Smith hasn't played and missed at many balls.

There was one from Jimmy Anderson this morning and a couple of times he was drawn wide and played half-hearted shots away from his body.

The rest of the time he has just sat on the back foot and England haven't seen able to get him off it.

Curran to Smith. Six dot balls.

Stephan Shemilt
BBC Sport in Melbourne

Even the children in the MCG creche came outside to applaud Steve Smith's century.

I mean 23 centuries in 60 Tests is just utter madness. What a player. It took Justin Langer 105 Tests to score the same amount of hundreds.

A couple of runs to Marsh off Moeen, not that it matters now.

Should be six overs until the captains can agree to the draw.

Nathan, Oxford

Tom Curran on. A few singles follow.

The final ball is drive-able and Marsh obliges, picking up three through the covers.

Andrew Samson
BBC Test Match Special statistician

It is Steve Smith's 23rd Test hundred. It is his eighth against England and fourth at the MCG. It is only the third time he has got a second-innings hundred.

A more muted celebration from Smith than his previous tons this series - acknowledging the crowd with his bat and quick kiss of the Australian badge on his helmet.

Perhaps a reflection of the unfussy way he's gone about it, just grinding away and batting England out of contention.

Moeen sends down an anonymous maiden.

Eight overs until they can shake on the draw.

Ed Smith
Ex-England batsman on BBC Test Match Special

This has been the story of the series, the story of the winter - England bowling at the middle of Steve Smith's bat.