The 1970 World Cup in Mexico is often seen as the greatest tournament in football history. It was the tournament when Pelé won the trophy for a record third time, when Gordon Banks made the save of the century, and when Brazil routed Italy 4-1 in a final for the ages.

A year later, however, another football World Cup took place in Mexico. Once again, the Azteca was full for the final, with 110,000 fans crammed into the stadium.

Yet unlike Carlos Alberto's infamous thunderbolt of a fourth goal, few supporters have ever seen footage of, or even heard of this ground-breaking tournament: the original Women's World Cup.

Last week, I went to watch Copa 71, a remarkable new documentary film about this extraordinary event.

The film combines recently discovered archive footage and interviews with those who took part to tell the tale of the tournament, and how it has stayed all but unknown for so long.

It's a story that seems bizarre given the present-day success of England's Lionesses, winning the 2022 European Championships and reaching the final of last year's World Cup.

But for much of the twentieth century, women's football was banned in this country.

The sport had grown rapidly, particularly during the First World War, but in 1921, the FA deemed the game 'quite unsuitable for females and should not be encouraged', ordering clubs not to allow women to use their facilities.

That ban (which was echoed in most countries around the world) was only lifted in 1969.

Two years later, an England team took part in the Mexico World Cup.

The team was a ramshackle group of players, mainly in their teens, who went from playing in a park to a handful of spectators to crowds of 100,000.

The film charts their experiences and their expectations of returning home to find women's football finally on the map.

Instead, they were greeted with comments about their appearance and media ridicule: 'Don't laugh one day there may be a female Arsenal' ran one headline.

Harry Batt, who'd put the England team together, was blacklisted by the football authorities. FIFA, who had little interest in the women's game, moved quickly to shut any future tournaments down. It would be decades before an 'official' World Cup took place.

Today, the 1971 tournament still remains unrecognised by the footballing authorities, despite the final boasting the highest ever attendance for a women's match: Kicking Down Barriers, the official history of the women's game on the FA website, makes no mention.

With footage feeling like it is from a parallel universe, Copa 71 is a powerful attempt to set the record straight: a film both jaw-dropping and eye-opening at the same time.