The 17-year-old Carr Hill A Level student grabbed a dramatic 84th-minute equaliser after Lowestoft Town had held on to an 11th-minute lead gifted to them by and own goal from Kirkham's Phil Thompson – a looping header that fizzed over Pete Summerfield's outstretched arms and into the top right-hand corner of the goal.
But Walwyn's introduction 12 minutes from time contrived to turn the game on its head.
Mike Clark's long through ball split the Suffolk side's defence and Sean Paterson fed the young striker, who shrugged off a tackle to fire in at the near post and send 5,000 massed banks of Kirkham fans into raptures!
As if to rub salt into Lowestoft's wounds, he side-footed in the winner deep into injury time as he had done at Needham Market in the semi-final, following skipper Dougie Shaw's delightful through pass that saw 28-goal striker Paterson storm through the Lowestoft rearguard.
And unselfishly Paterson drew Town keeper Andy Reynolds off his line, flicked the ball right into Walwyn's path and the Vase was on its way to Lancashire!
But the end result was nothing more than Kirkham & Wesham deserved, playing their last ever game at the home of English football before being rebranded as AFC Fylde.
Young Walwyn said later: "The dream was to score at Wembley but twice wasn't in the script."
Walwyn, still studying for his A levels in the hours building up to the final, admitted it was a dream come true.
Boss Mick Fuller, who led his side to a unique treble of Second Division Trophy, promotion to Vodkat division one and the FA Vase said later: "This is the original fairytale. We were the better side today but we left it late.
"But it's all about winning and to win here in front of all these fans is absolutely tremendous. We'll all remember this day for the rest of our lives."
While the whole of Kirkham & Wesham will rejoice in this success, and young Walwyn will rightly get all the plaudits, this was a good-to-honest team performance from 14 lads who really found something extra when it mattered.
Walwyn's late double was a just reward after Kirkham had enjoyed the bulk of possession, and while Lowestoft will rue the final 10 minutes (including added on time), they really didn't create enough chances to put the game away after going in front to a rather fortunate goal so early in the game.
Paterson was voted man of the match, and that was as much recognition for his unselfish late pass that won the game as for his 29th-minute effort that came back off the crossbar and keeper Reynolds.
Mark Wane had a shot blocked on the line 10 minutes later by Town defender Neil Plaskett, who had an outstanding day in the Lowestoft defence amid a torrent of Kirkham pressure.
Plaskett's late lunge to deny Paterson saved his side – at least until those dramatic last six minutes and added on time.
Lowestoft's star man Jamie Godbold admitted later: "We were six minutes from glory but that's how things go sometimes in football.
"Naturally we are all gutted by this – but we will be back."
For Kirkham & Wesham, Wembley was their last hurrah. Now the aim is for AFC Fylde to take them onto new heights.
Chairman Dai Davis added: "I thought that we thoroughly deserved it and l'm so pleased for everyone connected with the club who has worked so hard for this.
"What Mick (Fuller) and his management team have achieved is nothing short of miraculous – the Vase was the icing on the cake."
Davis was later presented with a belated 60th birthday cake, four days after he celebrated the milestone.
The whole day was mind-blowing and will never be forgotten by those fortunate enough to have witnessed it.