Bell first took guard with the hosts 28-3 after both openers had gone lbw and Kevin Pietersen caught behind, as Ryan Harris (3-43) took two wickets in the same over.
As at Trent Bridge last week, where as yesterday he made 109 – a pivotal contribution to England’s 14-run victory in an epic Test – Bell once again barely played a false shot.
But after Steve Smith (3-18) kickstarted a second rush of wickets with his occasional leg-breaks, deep into the evening session, England’s 289-7 was still under-par on a blameless surface in this second Investec Test.
Bell completed his five-hour hundred in a 144-run fifth-wicket stand with Jonny Bairstow (67), having first added 99 for the fourth with Jonathan Trott (58).
By the time he fell in Smith’s first over, caught at slip pushing forward to one that turned and bounced from a perfect length, Bell had added a century here to the ones he made in the last two Tests against Australia – at Sydney in 2010-11 and then in Nottingham.
He also became the eighth Englishman to score 1,000 Test runs at Lord’s, and his 19th hundred takes him level with Sir Len Hutton in the all-time list of his country’s most prolific centurions.
Of more pressing consequence, though, was the value of his chanceless innings here to England’s prospects of consolidating their 1-0 series lead.
They were far from encouraging when, after winning the toss on a glorious morning, Alastair Cook, Joe Root and Pietersen departed in the space of 11 balls.
Cook and Root’s dismissals were notable for extra context, the England captain falling to Shane Watson after Michael Clarke surprisingly brought the economical medium-pacer into the attack to replace James Pattinson for only the fifth over, and the young Yorkshireman going after another marginal DRS procedure.
Cook had got England under way with a boundary from the second ball of the match off Pattinson and was soon into double-figures.
After Pattinson appeared to be put off by the effect of the slope from the Nursery End and conceded 12 runs in his two initial overs, Clarke wasted no time summoning Watson.
He had taken 5-35 in his last Test match here, against Pakistan in 2011, and was in the headlines already this week over his reported strained relationship with his captain.
Whatever the reason for his early call-up to bowl, Watson did the trick with only his second delivery – pinning a tentative Cook lbw in the crease.
Root was hit in front too in the next over.
He decided to go to DRS, such a vexed process throughout most of the first Test, yet had to go anyway as ‘Hotspot’ revealed contact with the bat but no compelling evidence it had taken place before ball hit pad.
After Pietersen too fell cheaply, to a Harris delivery which held its line up the slope, much was needed from Warwickshire pair Bell and Trott.
They responded with an assured partnership either side of lunch as the ball continued to swing, Trott looking set for plenty more after completing his half-century until he haplessly mistimed a pull at Harris to deep midwicket.
Bairstow was not especially convincing as Bell nursed him through the early stages of an innings which appeared to have foundered when the No 6 missed an attempted drive at Peter Siddle and was bowled off-stump.
Bairstow on 21, and England on what would have been 172-5, were reprieved, however, because the third umpire spotted a no-ball – and he was therefore still around to accompany Bell past his highly-skilled 203-ball hundred.
With Pattinson still struggling, conceding 16 runs in an over at the start of one quickly-aborted spell and frontline spinner Ashton Agar out of the attack with a leg injury, it seemed Siddle’s over-step would prove an especially costly turning point – until Clarke chanced another Midas-touch bowling change.
The second new ball was apparently only minutes away when Smith was called into the attack for the 77th over, and struck a huge blow almost immediately.
It was a deserving delivery which did for Bell, but Bairstow gave away his hard work when he pushed a low full-toss straight back into the leg-spinner’s hands.
Matt Prior then edged an attempted cut behind off Smith, and it was tempting to conclude that – despite another Bell masterclass – the advantage was Australia’s.