CARDIFF Castle had seen nothing like it.
It had stood, tall and proud, when the Romans arrived in the 1st century and when the Normans did a spot of conquesting in the years after 1066.
But it was clearly unprepared for the Invasion of the Terriers.
Hordes decked out in blue and white turned the castle grounds beneath the ramparts into an away version of the McAlpine Stadium.
There was so much blue and white face paint it was if Mel Gibson's make-up department from Braveheart had emigrated from Scotland to Wales .
The fans unfurled their play-off flags like battle standards and camped out in the morning sunshine, many hours before kick-off, to savour every last second of what was destined to be a memorable day.
They poured into the ancient Welsh capital city from off the M4 and from the railway station and even through the Welsh countryside.
The Bank Holiday shopping crowds seemed insignificant as Huddersfield headed west.
Just occasionally, you glimpsed a little cluster of yellow and blue; the Mansfield Town fans, not quite as noisy or ebullient as the boys and girls in blue and white, but equally determined to savour the occasion.
But there was no yobbishness, no antagonism, just good-humoured banter. It was one of those sunny, smiling sort of days.
Jon Stead, the former champion of the Blue and White Hordes, soaked up the atmosphere beneath the castle walls, signing autograph after autograph for Town fans delighted with the success of his move to Blackburn Rovers and the Premiership.
He said: "It's a fantastic day and I came down here early just to enjoy every minute.
"I must admit, I'm a little bit nervous, never mind the Town boys, but I spoke to one or two on the phone and they seem really up for the game.
"Mansfield are a good side, but I think Jacko can do it. It will round off a great season, not just for me but for the club. It's their time".
Another bunch with plenty of reason to celebrate were the McAliskey clan.
Mum Julia, of Golcar, has seen her teenage son John blossom into possibly the next Jon Stead; filling the striker's boots in Town's first team, alongside veteran Andy Booth, Town's folk-hero.
She had made her way to Cardiff and the sunshine by minibus with John's three brothers Michael, Paul and Neil, sister Debbie and other friends and relatives.
They wore their home-made Macca shirts with pride and Julia said: "It's been a dream come true for him.
"Neither us nor him expected him to be in the first team so quickly but he can take it all in his stride.
"I just want him to know we're right behind him".
Joan Ellis, of Stainland, had a confession: the Cardiff play-off final was her first-ever football match.
She made the 230-mile trip with grandsons Sam Pinchin (12), Jake Pinchin (9) and Liam Higginson (4) and admitted: "It's fabulous.
"We came down on Sunday and I've loved every minute of it.
"It's great to see people mixing together".
The North family, from Heckmondwike, had also made a full weekend of it. Long-time Town fan Michael, his wife Mandy and children Jessica (7) and Liam (9) had travelled down on Saturday, stopping overnight in Worcesterhsire and then Gloucstershire.
"The atmosphere is fantastic," said Michael. "I've followed Town all my life and taken Liam to games for the past three years and this is the best yet".
As the thousands made their way towards the stunning Stadium, the omens looked good.
A quick count among the souvenir sellers showed Town's flags, scarves and Jolly Jester hats selling twice as quickly as those of their Mansfield rivals.
Town fans commandeered many of the vantage points. The Cuba Bar, The Slug and Lettuce, The Queens Vaults became little patches of Yorkshire, just for a few hours.
And even the official programme sellers were clad in blue - with Yorkie on their jackets!
The Welsh Police were out in force and did have to step in to keep some groups apart as the day wore on. But in general they shared the good humour of the fans. It was that sort of day.
The Millennium Stadium itself, nestled right in the heart of the city, was every bit as special as expected.
Town's 23,000-strong army had the North End; the gaps, it had to be said, were high above the South End.
And the cacophony of sound that greeted Peter Jackson's side as kick-off approached was phenomenal, boosted by hundreds of air horns and klaxons.
The songs poured down across the massed ranks: Stand Up If You Love The Town, We Won The League Three Times In A Row and Peter Jackson's Barmy Army.
The tension was palpable, the despair so deep as chances went begging.
Mansfield "scored", with only minutes remaining. Blue and yellow went wild. But then the referee intervened and Blue and White could celebrate.
And hours after many had first set foot in Cardiff, Lee Fowler - a young man born in the city - took a penalty which made history.