Watford legend Heidar Helguson believes Iceland’s odds-defying run to the Euro 2016 quarter-finals has been long in the making.

Helguson won 55 caps for his home nation before retiring in 2011, and said "massive improvements" to football facilities in the country over the past two decades are now beginning to bear fruit.

The striker enjoyed two spells at Watford during a 14-year stint in England, after first arriving at Vicarage Road in 1999 and then returning on loan a decade later.

It was during that opening stint he became one of only two men to score against England in Iceland’s history, in a 6-1 battering by the Three Lions just before Euro 2004.

That was a record which stood until this week, when Ragnar Sigurdsson and Kolbeinn Sigporsson wrote themselves into Icelandic folklore with a goal each in a shock win over Roy Hodgson’s men in Nice.

They will now face France in Paris on Sunday for a place in the Euro 2016 semi-finals as their astonishing run continues – just five years after they were ranked 124th in the world, sandwiched between Liberia and Tanzania.

But the 38-year-old, who has been in France with his family to support their side, told the Watford Observer the squad’s progression since then has been no coincidence.

He said: “The last 10, maybe 15 years, in all our aspects of coaching and facilities there have been massive improvements across Iceland.

“Until then it wasn’t possible to train during the winter but now we have indoor arenas and things are much better.

“This generation competing now is the first, I think, that have really been able to take advantage of all those changes in infrastructure.

“All the Under-19s, Under-21s and other youth groups are really good as well. It has moved forward so much in the last 15 or 20 years.

“The way they are performing now is only going to help that. All the kids back home are watching and if this doesn’t make them want to do well and train hard, then I don’t think anything will.”

Helguson knows better than most how football in Iceland has changed. He scored 31 goals in 54 games in its top flight as a youngster in the mid-1990s, and went home – to work as a fisherman and hotelier – once he hung up his boots in 2013.

But even he was taken by surprise by the sheer ease with which the country, whose population is around three times that of St Albans, held off England in their last-16 victory on Monday.

He said: “I didn’t really expect us to win, but they showed what I and lots of other have seen over the past two years, and they keep on surprising.

“England hadn’t been great themselves in the group games, but they were still clear favourites.

“In terms of what won us the game, I don’t think it was anything specific, but we were much better in almost all aspects of our performance.

“It seemed like they [England] ran out of ideas fairly quickly. When it was 1-0 so early on I thought it could be bad news, but we managed to equalise very quickly after; when we took the lead they didn’t really create anything.

“We’ve gone into the games after deservedly beating Holland home and away and some other big teams. It breeds a winning mentality and that team epitomises that.”