Dele Alli has produced many exciting moments in a Tottenham shirt but few were more spectacular than his goal at Crystal Palace last season.

With six minutes remaining and the score 1-1, Alli controlled a headed pass from Christian Eriksen on his right knee and, with his back to goal, flicked it over the head of Mile Jedinak and despatched a volley from 20 yards into the bottom corner. Tottenham won the game 3-1.

Fifteen months after that “I was there” occasion, Alli returns to Selhurst Park tonight as the best young player in England and one of the most talented in Europe.

Alli is coveted by the wealthiest clubs but Tottenham insist he is not for sale and it would be no surprise to see the 21-year-old offered an improved contract in the coming months.

If Tottenham really are to overhaul Chelsea, seven points clear again at the top of the Premier League after last night’s 4-2 win over Southampton, they will need Alli in the vanguard. He has 20 goals this season, a fearsome record for a player who had scored only four times for his club by mid-December.

​Tottenham manager Mauricio Pochettino understands how rare it is to discover players as good as Alli, who joined Spurs from Milton Keynes Dons for just £5million in January 2015.

He believes, however, that there are plenty in the Football League capable of making the jump to the top flight, as Alli did from League One.

“In England there are a lot of talented players in the lower divisions,” said the Argentine.

“It is important to have a good network and to be able to identify them, because England produces a lot of good talent.

“Dele Alli was a player I had been following since I was at Southampton. When I got there, Paul Mitchell [former Saints and Tottenham recruitment chief] told me I had to watch two players at Milton Keynes: Dele and Brendan Galloway, the full-back who went to Everton.

“They were so young and with so much potential.

“Soon after I joined Tottenham, I went to watch the game between Milton Keynes and Manchester United in the Capital One Cup in August 2014. Dele was 18 at the time and played as a holding midfielder. After watching him, we were in love.”

Sam Allardyce, the Palace manager, has been working on a plan to stop Alli but believes his progress demonstrates the value of playing regularly in the Football League.

Alli made 88 appearances for Milton Keynes before moving full time to Spurs for the start of the 2015-16 season, when he was still only 19.

​Allardyce said: “We slip up in development in this country because all the boys go to the big clubs.

“They have fantastic facilities but the path to the first team is blocked so they lose competitive edge.

“Wilfried Zaha found it by getting in the first team here and Dele Alli did the same at MK Dons.

“You have to be so strong mentally at this level and playing in the Football League makes you understand what you need to do to be a top professional.”