ALEX HALES admitted it was "gutting" to get out six runs short of a maiden Test century as England pushed for a 3-0 series whitewash of Sri Lanka at Lord's.

Hales, who had been dismissed in the 80s twice previously in the series, got within striking distance of three figures when was trapped lbw on the back foot to Angelo Mathews.

The opener admitted he had a first Test ton on his mind but was satisfied to have played another major role as England set the tourists a ground-record target of 362.

"Of course it was on my mind," he said. "Looking at it now it's a pretty decent delivery, but I could have played it with a straighter bat.

"It was a gutting moment but it was a good ball, and I'd have taken that (94) at the start of the Test match."

Both Hales and Alastair Cook had collector's-item good fortune on their side, via DRS and playing conditions, before England declared on 233 for seven on day four of the third Test.

A especially unusual escape on 58 for Hales, thanks to an errant no-ball call by umpire Rod Tucker, brought a sideshow of minor controversy.

Sri Lanka draped a national flag over the team balcony as a demonstration of moral support for unlucky bowler Nuwan Pradeep (three for 37), then had to take it down at the request of MCC because it contravened ground rules.

Sri Lanka Cricket president Thilinga Sumathipala later confirmed the circumstances surrounding Hales' non-dismissal would be "reported to the International Cricket Council" – adding tour management were "very sad" about it.

The bottom line, however, was that – after Hales and Cook's sixth-wicket stand of 82 – England were able to set their opponents a ground-record target of 362 and had obvious prospects of a third successive victory, albeit one which will have to be harder-earned than the previous two.

To do so, on a pitch providing untypically variable bounce and sharp turn, they will need all 10 wickets on the final day after Sri Lanka closed on 32 for none.

Hales, who had twice previously in this series got within striking distance of a first Test hundred, finally departed almost on the stroke of tea after rain had prevented play until 2.40pm.

By the time he was lbw on the back foot to Angelo Mathews, the opener had used up his fair share of good luck in an innings which contained 10 fours and a six over long-on off Rangana Herath.

The strangest occurrence came when he appeared to have been bowled by a Pradeep shooter.

Tucker's mis-call provided the reprieve – one which stayed, because of an anomaly in current ICC protocol.

A front-foot line decision can be over-ruled by the third umpire to provide an escape route for a dismissed batsman, if the bowler has overstepped without initially being called - but the equal and opposite amendment is not yet in place.

Hales could not reasonably claim to have changed his shot in any way on the basis of a no-ball call on this occasion.

Pradeep was therefore robbed, by human error, of his fourth wicket.

Then in the next over came confirmation that nothing was going right for Sri Lanka when Cook went to DRS to overturn lbw on the back foot to Herath and simulation demonstrated impact with the left-hander's back leg was marginally outside off-stump.

For good measure, with Cook still only on 11, more turn down the slope would have seen him off lbw had Sri Lanka chanced their remaining DRS option.

The tourists had at least got rid of nightwatchman Steven Finn quickly, pinned in front lbw when Shaminda Eranga (three for 58) swung one up the slope after England belatedly resumed on 109 for four.

Hales was therefore reunited with his familiar opening partner Cook, the England captain fit to bat down at No.7 after recovering sufficiently from the bruised knee which forced him out of action the previous day.

Hales benefited from two thick edges down to third-man for boundaries off Eranga, and another mighty close call for lbw in between on the way to his 50.

He was again unable to convert to three figures, but provided the cornerstone nonetheless for England.

Cook subsequently had the freedom to launch only the 11th six of his record-breaking Test career, high over long-on off Herath – and mix in some uncharacteristic, nifty limited-overs-style novelty shots too – before declaring one short of his own 50.

It was to no immediate avail, as Dimuth Karunaratne and Kaushal Silva then closed out a day halved by bad weather to only 45 overs.