As Cristian Romero pulls on the famous red shirt, he hums the words to North London Forever before making his way into the tunnel at the Emirates Stadium.

As the team walk out onto the pitch, Romero high-fives mascot Gunnersaurus, who points to the Argentinian’s brand new ‘Once a Gooner, always a Gooner’ tattoo on his right calf and gives a thumbs up.

Unlikely? FantasyLand? Well, if Arsenal pursue their surprise interest in the 28-year-old centre-back, perhaps not.

Not that Tottenham Hotspur appear willing to consider an approach from their neighbours and bitter rivals for their captain, let alone sanction a sale.

He may have been born in Cordoba, northern Argentina, but after five years at the Tottenham Hotspur Stadium, the notion of Romero being allowed to head the four miles south to the Emirates feels extremely problematic at best, sacrilegious at worst.

And yet, it wouldn’t even be the most controversial transfer in the history of the Arsenal-Spurs rivalry, let alone English football and certainly not globally. It would, though, add to the list of highly-disputed mooted moves that never happened.

“I was asking myself why he’d choose Arsenal when you know how much it’s going to affect your personal life,” ex-Spurs defender Stephen Clemence previously told The Athletic. “That’s what surprised me most about his decision. You turn your whole life upside down with a move like that.”

Sol Campbell was heading towards Tottenham-legend territory. Born a 30-minute drive from White Hart Lane in the Plaistow district of east London, academy graduate Campbell was still a teenager when he made his first-team debut for Spurs and would blossom into one of the Premier League’s best defenders, an England regular, their captain who lifted the League Cup in 1999 and a player who made more than 300 appearances for them.

Then, aged 26, he left on a free transfer to further his career ambitions. Disappointing, yes, but understandable. Inter of Italy and Spain’s Barcelona were possible destinations, but instead Campbell shocked English football and caused unimaginable consternation and fury… by joining Arsenal.

Spurs fans took this very, very well.

They hung an effigy of Campbell from a lamppost on Tottenham High Road, flooded their stadium with ‘Judas’ banners when he returned as an Arsenal player, threw drink bottles and missiles in his direction and endlessly chanted ‘scum’, among many worse words. His new Arsenal team-mates had booed Campbell in training to prepare him for the reception but, well, nothing could quite compare to the abuse he took.

Tottenham fans direct their anger at Sol Campbell in November 2001 (Tom Jenkins/Getty Images)

“In hindsight, I’m not sure if I would sign him again, bearing in mind the difficulties he faced,” Arsenal’s then manager Arsene Wenger later said.

It was the most controversial transfer in modern English football history, but one Campbell could justify via the two Premier League titles and three FA Cups he won in six seasons with Arsenal. “Spurs fans have not forgotten it, but it was the best thing I could have done for myself,” Campbell said.

Fellow defender William Gallas may have gone in the opposite direction to Tottenham (also on a free) a few years later, but nothing has compared to Campbell’s move since.

Imagine Bruno Guimaraes ditching this week’s Arsenal move to join Sunderland from Newcastle United instead, or Erling Haaland swapping Manchester City for neighbours United and you’d have something comparable.

The latter switch is not without precedent, though.

Carlos Tevez sort-of swapped Old Trafford for the Etihad Stadium in 2009; he had won two Premier League titles in two seasons having been loaned to United for two years from West Ham but, having elected not to join the club permanently that summer (despite United wanting to sign him), he instead went to City.

This was before their dominance era, so the old noisy neighbours wanted to make a big song and dance out of the deal and erected a huge ‘Welcome to Manchester’ billboard to reflect what would soon be a changing of the guard in the city.

Manchester City’s ‘Welcome to Manchester’ billboard after signing Carlos Tevez angered Sir Alex Ferguson (Dave Thompson/PA Images via Getty Images)

It was a marketing idea laced with genius, although United manager Sir Alex Ferguson didn’t quite see it that way, calling the stunt “stupid and arrogant”.

The Manchester rivalry is fairly hate-filled, so Wayne Rooney’s dalliance with City when he submitted a transfer request at United in 2010 was pretty controversial, ditto Cristiano Ronaldo’s flirtation with the Etihad in 2021 before he returned to Old Trafford after more than a decade with Real Madrid and Juventus. But it’s nothing compared with United’s rivalry with Liverpool.

Players swapping one of those clubs for the other is almost unheard of, to the extent that it has not happened since 1964, when Phil Chisnall moved to Anfield for £25,000 ($34,000) when the rivalry was devoid of the intensity that fills it now.

Even playing for both clubs in a career is rare, with only two men doing it in the Premier League era: Paul Ince (in 1997, two years after leaving United for Inter) and Michael Owen, with the latter seen by many Liverpool fans as a traitor for moving to Old Trafford in 2009, five years after leaving Anfield for Real Madrid.

Only one player has come close to leaving one for the other in modern times, although given United’s staunch opposition to the mooted deal, it perhaps never came that close at all.

Defender Gabriel Heinze wanted to leave in 2007, having lost his place in the team to Patrice Evra. Liverpool were his preferred destination and submitted a bid of £6.8million, which they believed met a minimum-fee release clause.

But United rejected it, and the dispute became bitter. Heinze believed the offer should legally have been accepted, so it went all the way to a Premier League tribunal, which ruled in United’s favour. Heinze never played for them again, eventually joining Real Madrid that same summer.

The Argentina international defender, now a coach at Arsenal, came to regret the saga. He said in 2011: “I was aware of the rivalry, I knew the risk of going from Manchester to Liverpool and what it means. I hope it doesn’t tarnish the way they (supporters) see me and they will remember the three years I had in the team.”

Given how unpopular United are with many other fanbases, moving there can destroy a legacy, like when Robin van Persie joined from Arsenal in 2012, or Alan Smith, who was Leeds United through and through before he broke Yorkshire hearts when signing for the team they despise like no other in 2004.

Steven Gerrard had his Liverpool legacy and connection in mind when he rebuffed Chelsea in 2005 after a long, protracted dalliance with the best team in England at the time, albeit he had just won the Champions League under Rafael Benitez.

“I’d have regretted it for the rest of my life,” Gerrard said recently of moving to Stamford Bridge.

“I went to see my dad and my brother, who are two Liverpool fans, and they completely took all the external out of it and just said, ‘If you go and win two or three Premier Leagues, or a European Cup, with Chelsea or Inter Milan, or Real Madrid, will it be good?’

“And I went, ‘Yeah, of course it will be good, because you’ve won’. They said, ‘But will it be good or better than if you win one more trophy with Liverpool?’ And I said, ‘No, I’d feel better to do it with Liverpool’. They said, ‘Well, just make it all go away’. And it all went away.”

Transfers just do not happen between certain clubs, like Glasgow’s big two Celtic and Rangers, for example, given their deep-seated rivalry which encompasses far more than football.

Rangers famously had an unwritten policy against signing Catholic players, which was smashed in 1989 when former Celtic striker Mo Johnston joined from French club Nantes. It was hugely controversial.

Johnston’s agent Bill McMurdo later said: “After the signing, Maurice and I had security with us 24 hours a day. I had people stay in my house for six months, and Maurice had a minder with him all the time.”

It takes an audacious player to sign for both Celtic and Rangers during their whole career, with Kenny Miller and Steven Pressley among a very small post-Second World War number to have done it.

It’s a similar story with Barcelona and Real Madrid in Spain. Only a handful have moved directly between the clubs in the past 50 years, such as Argentine striker Javier Saviola in 2007 (he joined Madrid on a free transfer after his Barca contract expired) and Spain midfielder (and now Paris Saint-Germain head coach) Luis Enrique, who went the other way in the same circumstances in 1996.

By far the most prominent and hate-filled such transfer was when Luis Figo made a then-world-record £37million move to Madrid in 2000. The Portuguese forward had won La Liga with Barca in 1998 and 1999, but that was not enough to stop him ditching the Camp Nou for the Bernabeu, leaving a trail of destruction in his wake.

Missiles rain down on Luis Figo at the Camp Nou in November 2002 (Firo Foto/Getty Images)

When he returned to Camp Nou in a Madrid shirt, glass whisky bottles were thrown onto the pitch by angry fans, and every time Figo took a corner, the game had to be halted due to the barrage of missiles hurled in his direction.

“When we warmed up and saw that atmosphere, I’d have been happy if the referee decided to call off the game,” then Madrid full-back Roberto Carlos said.

It got worse two years later, when a pig’s head was thrown at Figo during a Barca-Madrid match.

Romero may or may not have it that bad at the Tottenham Hotspur Stadium as an Arsenal player if he makes this move, but it might be wise not to find out.