Alastair Cook claimed Sri Lanka "crossed a line" between what is and is not acceptable in international cricket when Sachithra Senanayake ran out Jos Buttler at Edgbaston.

In a Royal London Series decider which Sri Lanka won by six wickets, the controversial dismissal of Buttler, when backing up at the non-striker's end, in England's lacklustre innings of 219 all out was the unmistakeable flashpoint.

The tourists' captain Angelo Mathews emphasised, after half-centuries from Lahiru Thirimanne and Mahela Jayawardene, had ensured a successful chase and 3-2 series win, that he would have no hesitation doing the same thing again.

Mathews, jeered along with Senanayake by a partisan crowd, explained that Buttler and Ravi Bopara had been pinching yards too in their century stand in England's narrow defeat at Lord's on Saturday - hence Sri Lanka's decision to make sure they invoked the rules so that it did not happen this time.

Cook, however, said: "In my opinion, there's a line - and I think that line was crossed today.

"I was pretty disappointed with it. It was a pretty poor act."

He conceded he has not yet had to make a similar call, so cannot be totally sure how he might react.

"You don't know quite in the spur of the moment about it, but you know emotion can get the better of you," Cook added.

"Until you are put in a situation like that you don't know how you would handle it. (But) I'd hope to think I wouldn't do it."

Cook does not believe Buttler was trying to take an unfair advantage.

"If he was properly trying to steal a single, I could possibly understand it," Cook said. " But he was half a yard out of his crease."

England's wicketkeeper-batsman was aghast at the turn of events, and ill-feeling appeared to persist into Sri Lanka's innings.

"He was angry, like you would be," said Cook.

"But I suppose, if he was in his crease, you wouldn't have had that problem.

"You could say it was dozy from Jos ... you can look at it whichever way you want."

Mathews had no doubt about who was to blame.

"He was taking unfair starts, not only in this game but the last game as well, so we gave him two warnings in the spirit of cricket," Mathews said.

"I don't know how to stop a batsman from doing that continuously, but we had to go for it.

"I would probably stick by it, because what we did was completely within the rules."

The vastly experienced Jayawardene is even more convinced Sri Lanka did the right thing.

"We gave him a fair chance twice - before the first warning as well, we told the umpires that they're taking too much of a lead," Jayawardene said.

"We had to do that, because they kept doing it.

"At Lord's, they took 22 twos in the last 12 overs. Ravi and he ran riot, and most of the time they were taking starts - which was not legal by the written law.

"We warned the umpires, warned them. They didn't listen to us, so we had to take the right steps.

"The umpires said they would handle it ... but obviously didn't."

Sri Lanka have developed a reputation in recent years for fair play.

"We have always tried to play in the right spirit," added Jayawardene.

"But if the other teams are not playing with the right spirit, by the law, we had to do this unfortunately.

"We have maintained a high-class standard, and won the 'Spirit of Cricket' award for doing that quite a few times.

"He was told not to take a start, and then warned again. So it was the third time - fair enough, I think.

"We all need to play by the rules."

The tourists were already galvanised before the start of play by the decision at Lord's, of umpires Ian Gould and Marais Erasmus, to report Senanayake for a suspect action.

Jayawardene said: "We are disappointed as a group. That happens when a team-mate is being accused.

"He's played for a couple of years with us now, in international cricket ... but we'll take it with our heads high.

"Unfortunately the skills of our guys, good skills ... are being questioned.

"It was a big motivation factor (for us today). Sachi is a fantastic young player ... very cheerful and keeps everyone happy ... and as a team we'll walk through."