It may well be a first at St James' Park. Though Julen Izagirre will be decked out in the colours of his beloved Athletic Club on Wednesday night, the Basque will also have a Newcastle United scarf draped around his neck. "It's so confusing for me," he said before the sides' meeting in the Champions League. "I have sat in the home end in all of the previous occasions I have watched Newcastle at St James', but I will now be in the away end for the first time in a stadium where I support the local team too. "I don't know how I will feel when the game is being played because my feelings towards both clubs are so strong that I think I will suffer more than enjoy it. I don't want either of them to lose."

This is the legacy of the clubs' most recent competitive meeting, in 1994, which was at the heart of Izagirre "falling in love with Newcastle", after supporters struck up a strong bond. Izagirre may have only been six at the time, but he felt the impact of that night after his father, Mikel, was among those in attendance at Athletic's San Mames stadium as the home fans invaded the pitch and applauded the away end following a 1-0 win.

It was a moment that even left a lasting impression on those who played in the Uefa Cup second-round tie, such as forward Gontzal Suances, who scored for Athletic in the first leg at St James', before lining up for his boyhood club in the return fixture in Bilbao. "It's a joy that my dream of playing for Athletic is also linked to being part of a story as beautiful as the one forged with Newcastle," he said.

The feeling was mutual. Newcastle may have been knocked out, on away goals, but fan Tony Waters still speaks fondly about this particular trip because of the reception locals gave the travelling support. "They wouldn't let you spend anything," he said. "I'm not joking. I've followed Newcastle all over Europe and I came back with as much money in my pocket as I went with [on that trip]. "They were so kind and laid the red carpet out for us. They wouldn't let you buy a drink."

The seeds had been planted on Tyneside a couple of weeks previously after Newcastle supporters gave their Spanish visitors a warm welcome. It was so memorable, even Atletico players like Suances later learned how the fans had "bonded very well there", which led to Newcastle supporters being "repaid for everything they had given".

And it is easy to see why they got on. Both Basques and Geordies have a proud local identity and are immensely passionate about their football clubs. Bilbao is also a "very British city", in the words of Athletic supporter Mikel Izagirre, the father of Julen. "You hear that comment all the time from different fans, different places," the 72-year-old said. "You can see it if you walk through the city and if you visit San Mames and watch an Athletic game. Bilbao has a very strong British cultural influence."

That influence, which can still be seen in the architecture in part of the city, is a product of the industrial revolution. In the late 19th and early 20th Centuries, British ships would bring coal to Bilbao and return with iron and steel. Alongside came thousands of miners and engineers, many of them from north-east England, who brought with them one of the country's greatest exports - football. At the same time many students travelled the other way to study. When they returned, they too had caught the bug.

Which is why, when the club were founded, it was decided to use the English word 'Athletic' in their name rather than the Spanish 'Atletico'.

The momentous trip came during Newcastle's first European campaign since 1977. It was also their first since the ban on English clubs playing on the continent after the Heysel Stadium disaster had been lifted in 1990. There was still a reasonable police presence in Bilbao on what was a national holiday. Supporter Karl Pedley recalled how Newcastle fans were accompanied into San Mames by "full riot police, some of whom were armed". However, just a few minutes into the game, he noticed how "a number of them had sat down with their helmets and pads off, and were enjoying what we were doing".

There was no edge, even after Newcastle were defeated 1-0, and Athletic fans invaded the pitch and sprinted towards the away end to applaud the travelling support. Newcastle supporters responded by chanting "Athletic! Athletic! Athletic!" - but that was not the end of the matter. "The police held us back for a short while and took us down a long concrete staircase into the main road," Pedley said. "All we could see at the bottom was this mass of red and white. "They brought us down in single file and let us go. We thought 'oh, here we go.' But all the Athletic fans wanted to do was shake your hand, pat you on the back and take you to a bar. It was as if they were like 'adopt a Geordie'. "I don't think there was anyone in a Newcastle United shirt who didn't get fed and watered that night. They were just really appreciative that we were enjoying their city."

Chants were exchanged as Newcastle fans taught Athletic supporters - among others - "walking in a Keegan wonderland" and "he gets the ball and scores a goal, Andy, Andy Cole". Shirts and scarves were even swapped and this remains, possibly, the only occasion when a number of Newcastle supporters wore red and white, which are also the colours of bitter rivals Sunderland. One such Athletic shirt remains a cherished memento from an away day that Newcastle fan Philip Long will never forget. "It's still in the wardrobe with a couple hundred of my Newcastle tops," he said. "I'll never let go of it."