Stuart Broad joked he does not know the rules after the TV umpire ruled Australia's Steve Smith was not run out in the fifth and final Test at The Oval on Friday.

Substitute fielder George Ealham, son of former England international Mark, sprinted in from the rope as Smith sought to complete a risky two and hurled in a hard, flat throw that left the diving batsman short of his ground.

It brought back memories of the 2005 Ashes, when the unknown Gary Pratt ran out Ricky Ponting, but a careful review of the replays appeared to show England wicketkeeper Jonny Bairstow nudging one of the bails out of its groove a fraction of a second before taking the ball.

Smith had been on his way to the pavilion when he turned on his heels, with TV umpire Nitin Menon ruling in his favour.

The Marylebone Cricket Club (MCC), cricket's lawmakers, posted a clarification of the rules on its social media channels.

Paceman Broad, who took 2-49, admitted he was non-plussed.

"I honestly don't know the rules," he said. "I think there was enough grey area to give that not out. 

"What are the rules? Was it the right decision? It looked sort of benefit-of-the-doubt-type stuff.

"First angle I saw I thought 'out' and the side angle looked like the bail was probably dislodged."

Smith went on to make 71 as Australia reached 295 at the end of the second day, 12 runs ahead of England's first-innings total of 283.

Australia's star batsman said initially he thought he might be out but a second angle put doubt into his mind.

He was asked whether he knew the rules.

"Don't the bails have to come out off the stumps, out of the grooves or something as far as I know?," Smith replied.

"But you've just got to go off the umpire and what he says and fortunately for me he said 'not out'."

The MCC said in its post: "The wicket is broken when at least one bail is completely removed from the top of the stumps, or one or more stumps is removed from the ground.

"Tom Smith's Cricket Umpiring and Scoring, MCC's official interpretation of the laws of cricket, adds: "For the purposes of dismissal –- a bail has been removed at the moment that both ends of it leave their grooves." 

England, trailing 2-1 after the rain-affected draw at Old Trafford, must win this match to level the series.

Holders Australia, seeking their first Ashes series win in England since 2001, have already retained the urn.

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