London, Jul 20: Opener Joe Root scored his second test century shortly after tea on the third day of the second test against Australia as England took a commanding lead of 443.
England was 210-4 Saturday after 87 overs with Root undefeated on 111.
Ian Bell was 36 not out after surviving a controversial claim for a catch that appeared to be out. Bell was given not out by third umpire Tony Hill when, on 3, he edged Ryan Harris to gully fielder Steve Smith.
Australia would need to set a new record for the highest fourth innings run chase to win a Lord's test, which currently stands at 344-1 by West Indies in 1984.
England was in charge of the match having made 361 in its first innings before dismissing the Australians for a below-par 128 on Friday.
It was a mature innings by the 22-year-old Root as he remained patient amid some accurate bowling from the Australians, who attempted to choke off his runs and slow the game. At tea he was on 97, having faced 237 deliveries with 11 boundaries.
England survived the morning session without losing a wicket, as nightwatchman Tim Bresnan required 30 balls to score his first run but eventually managed a well-crafted 38.
He was caught by Chris Rogers at midwicket off a bouncer from James Pattinson, to bring Bell to the crease. Yorkshire pair Bresnan and Root added a precious stand of 99 that frustrated the tourists and added to England's dominant position.
England is seeking to win its third straight Ashes series.