Robin van Persie’s decision to switch to Manchester United last summer was vindicated by his leading role in their title triumph

It must have been a strange phone call. On the eve of the start of the season last August, Arsene Wenger and Sir Alex Ferguson had a brief conversation in which the Arsenal manager agreed to sell his captain and top goalscorer to a man who was once his sworn enemy.

“I remember Arsene Wenger saying to me ‘he’s better than you think’ when we concluded the deal. He was right,” said Ferguson after watching Van Persie’s hat-trick destroy Aston Villa and deliver a 20th league title to Old Trafford on Monday night.

The £24million deal was a double triumph for Ferguson. Not only had he prised away the best player from a club and manager he used to regard as a great rival, but in doing so he had trumped the side who had left a bitter taste in his mouth by stealing their title the previous May – the noisy neighbours of Roberto Mancini’s Manchester City.

It is now being hailed as Ferguson’s greatest transfer coup since persuading Eric Cantona to cross the Pennines from Leeds to Manchester United in 1992, a £1.2million bargain that ushered in the first of the Scot’s 13 title triumphs in the Premier League’s debut season.

“When you identify a great player coming to the end of his contract, you go for him no matter who,” said Ferguson on Monday of his decision to buy Van Persie.

“In terms of impact he has made as big an impact as any player I can imagine. Cantona was an incredible impact player, I’ve had some great strikers, maybe 10 great strikers.

“We had an expectation of him [Van Persie]. He was sensational last year [for Arsenal], and he has never disappointed us. He has been unbelievable, his early form was fantastic. He had a dry spell, as most strikers do, but he has come back from that and he was unbelievable tonight.”

Arsenal fans were probably tempted to switch channels as Van Persie’s second goal, a trademark searing volley, crashed past a startled Brad Guzan in the Villa goal.

“It was goal of the century for me, it was marvellous” purred Ferguson. “The technique with his head down, over the ball and just perfect timing, it was a magnificent strike.

“He scored exactly the same goal for Arsenal. He is in his mature years and winning the league tonight meant a lot to him.”

That, of course, was the key to Van Persie’s decision not to renew his contract last summer.

He had made his intentions painfully clear during the previous season, in which he scored 37 goals in all competitions, scooping both the PFA and Football Writers’ Player of the Year awards.

It was a summer in which Van Persie would turn 29 years of age and, after eight seasons playing for Wenger – the last seven of which had ended without a winner’s medal – and with one year remaining on his Arsenal contract, his mind was made up.

“I’ve thought long and hard about it, but I have decided not to extend my contract,” said Van Persie, making it chillingly clear with his statement in early July he would not be staying on.

“It has again become clear to me that we in many aspects disagree on the way Arsenal FC should move forward.”

That was effectively that. But City had been courting Van Persie all season, Mancini talking about him in glowing terms as the Dutchman’s goals rained in.

However, after some extended wrangling that also involved an offer from Juventus, Van Persie chose United and the deal was finally done on August 17, just 24 hours before the start of the current season.

Ironically, the details of Van Persie’s transfer included a further £1.5m payment if United were to win a Premier League or Champions League during his time at the club.

United will now hand over that money all too readily, and there will be handshakes and smiles in the directors’ lounge on Sunday.

But there will be a hollow feeling for Arsenal on Sunday, not only in accepting that payment but also in forming a ‘guard of honour’ for the new champions, and watching their former player and captain grace the Emirates turf in a different shirt.

Just like Samir Nasri and Gael Clichy with Manchester City last season, and Cesc Fabregas with Spanish champions-elect Barcelona, a player who was moulded, modified and made at Arsenal has had to leave to fulfil their ambitions of success.

For Van Persie the justification has been swift, and unequivocal. A championship medal already, and how many more to follow? He can enjoy his first Emirates return on Sunday, knowing his ‘big decision’ from a year ago was unquestionably correct.

Follow Paul Chronnell on Twitter @GazetteGooner