Three months on the concept of Leicester City being the defending Premier League champions still does not seem real. There will be reminders of it in the coming weeks, starting with the Community Shield against Manchester United on Sunday. But despite this being Leicester’s first top-flight title win and having never won the FA Cup, this will not be their first appearance in the season curtain-raiser.

In 1971 Arsenal won the Double, the second club in the 20th century to do so, but whereas that would usually confirm their place in the Charity Shield, they had other plans for early August. Rather than take part in what is the traditional season opener, Arsenal played a series of friendlies: two against Benfica (home and away), and on the day faced Feyenoord in Rotterdam.

During their march to the Double they had been forced to cancel a friendly with Benfica, under pressure from the powers that be wanting their players available for the home internationals. “That left a nasty taste in the mouth,” said Bob Wall, Arsenal’s secretary at the time, so the only way to wash it away was the palate-cleanser of two games in August and a trip to the Netherlands tacked on.

So, with the champions and FA Cup-winners indisposed, who would get the honour of playing in the Charity Shield? Liverpool were a logical choice, having lost the Cup final to Arsenal the previous May, but beyond that the options were wide and varied. Leeds (the runners-up in the league), Tottenham (the League Cup winners) and Chelsea (the Cup-Winners’ Cup holders) were considered, but in the end they plumped in favour of Leicester, the Second Division champions.

Why Leicester? Well, no one seems to have a definitive idea, beyond “they were as good as anybody else” and “they were available”. Chelsea were initially keen but were overlooked, Tottenham were on tour in Scotland, and although Leeds were upgrading their ground so hosting would have been a problem, they probably would not have been allowed to anyway.

They had spent most of that summer arguing with the Football Association over a four-game ban on staging games at Elland Road, placed on them after the previous season’s debacle at West Bromwich, when Jeff Astle scored a goal that initially seemed to be yards offside. Fans invaded the pitch, Don Revie had some harsh words to say about the referee, and Barry Davies declared the Leeds supporters, players and manager had “every right to go mad” about the goal, despite it being perfectly legitimate. Safe to say, Leeds were not in the FA’s good books.

And so to the game. Held at Filbert Street (Anfield was unavailable because of ground redevelopment), a sunny day in August saw 25,104 show up. There was plenty to look forward to: this was Leicester’s first game against top-flight opposition after winning promotion, and they had a new manager in Jimmy Bloomfield. Frank O’Farrell, who had masterminded their successful promotion, had been tempted away by Manchester United and after Don Howe declined to be interviewed, Bloomfield left Orient for the east Midlands.

It would – in hindsight – turn out to be a pretty big day for Steve Whitworth. A lifelong Leicester fan, the young right-back made his first-team debut the previous season and was established in the team by the time promotion was won. Whitworth scored the only goal of the game, capitalising on a spot of penalty area pinball to tap home from inches out.

“I made a real long, overlapping run,” says Whitworth now, “I got into their penalty area and just slid the ball across their six-yard box.” Whitworth’s cross was aimed for the centre-forward Rodney Fern, who nipped in just ahead of Tommy Smith but could not get a proper effort on goal, the ball dribbling back towards the post. The goalkeeper, Ray Clemence, initially went for the cross, then stopped and changed direction, scrambling and diving back, presumably thinking no one would be behind him. Not quite.

“The ball just sort of popped out, and for some unknown reason I’d carried on running,” Whitworth says. “I tapped it in with my left foot, and if you ever watched me play my left foot was purely for standing on, I assure you. It was amazing how it all happened.”

It would turn out to be a notable strike because it was the only goal Whitworth would score for Leicester, a club he left eight years and more than 350 games later. “I didn’t even realise that as the years went by,” he says. “It wasn’t something that ever got mentioned.”

“Already at home” read the headline in the Guardian, while Brian Moore in the Times was particularly effusive about Leicester’s showing, writing the performance “suggests more a coming season of achievement than one of mere survival”. The top-flight newcomers seemed to cope well with a Liverpool side who featured Clemence, Steve Heighway, John Toshack, Emlyn Hughes and Ian Callaghan. According to the Leicester Mercury, they “might have scored four had it not been for the fine goalkeeping of Clemence”.

Leicester’s Jon Sammels, bought from Arsenal that summer, was the most impressive player on the pitch in the 1971 Charity Shield. Photograph: Colorsport/REX/Shutterstock

Seemingly the most impressive performer was a man who otherwise might have been in Rotterdam: the only new signing to play for Leicester that day was Jon Sammels, a midfielder purchased from Arsenal, whom the Guardian’s match report described as being “the main driving force” behind Leicester’s win.

Bloomfield was particularly delighted, largely with himself. “I saw Arsenal beat Liverpool [in the Cup final] and I thought then that if ever a team of mine played them I would know the tactics to adopt,” he sagely informed the Daily Mirror. “In the final, Liverpool were caught by the long through ball. We planned to take advantage of this – and it worked. I told the players if we could get the square Liverpool defence turning, it would be our best form of attack.”

Leicester became only the second club to win the shield who had never won league or cup, the other being Brighton in 1910, although there was not much fanfare about the achievement. The shield was presented away from the public eye, below the stands at Filbert Street, partly because of some crowd trouble at a testimonial game that year, when the Second Division trophy was due to be presented on the pitch but some fans invaded the turf.

It is worth noting that back then the Charity Shield was not quite the event it is today. In its early days the format was fluid, early incarnations featuring a game between professionals and amateurs, the winners of the Football League and the Southern League, while in 1950 an England side took part and when Tottenham did the Double in 1961, they played an FA invitational XI. It was not held at Wembley either and its shift to the grand old stadium was when people started taking it more seriously.

A little too seriously as it turned out, as the first time it was held there, in 1974, Leeds faced Liverpool and Billy Bremner and Kevin Keegan marked the occasion by fighting and ripping their tops apart when they were sent off.

The move to Wembley was partly in response to increasingly lukewarm attitudes to the match: after Arsenal opted out in 1971, the following year the champions, Derby, and cup winners, Leeds, didn’t fancy it, so fourth-placed Manchester City and the Division Three winners Aston Villa played; the year after that, Liverpool and Sunderland were not keen so the ever-willing City (11th in the First Division) and Burnley (Second Division champions) stepped up.

For Whitworth, the Liverpool game would represent a snapshot of youthful exuberance. “Everything was just easy peasy,” he says. “I got in the team, had a great season, played in the Charity Shield, scored the goal – it all seemed like life was supposed to be, really. I was so bloody naive in those days. You’re just free and do what you want, and it’s only later when people start picking faults in you.

“Later on I became far more disciplined and start thinking maybe a bit too much about the team, where you should be on the pitch and so on, instead of just bombing forwards, which is how I got into the team in the first place.”

At that stage, it might have seemed like games such as this, brief moments in the spotlight where they defeated the finest teams in the land, were as good as it would get for Leicester. Their only previous major honour was the League Cup in 1964, a cup they would win again in 1997 and 2000. Should they win the shield again this year, it will be sweeter because of what came before.

As for Arsenal, they lost the friendly in Rotterdam 1-0, and the Times reported that the “60,000 crowd was left disappointed”. They might as well have stayed at home.