By David Cornock
BBC Wales parliamentary correspondent
Lord Snowdon said the event went "swimmingly"
At first glance it looks like any other photographic studio, even if it is based in a smart house in a classy area of London.
The family snaps on the desk offer a clue that this is no ordinary photographer. They are signed by, among others, the Queen and Diana, Princess of Wales.
The man who took them is best known for marrying into the Royal Family and for his photographic work. But 40 years ago, Lord Snowdon played a central role in the investiture of the Prince of Wales, his nephew through his marriage to the Queen's sister, Princess Margaret.
Now 79 and rather frail, he shows me his immaculate scrapbook of the occasion, with newspaper cuttings, photographs and the "original scribble" of the design for the dais used for the investiture.
"It looks rather like Henry V, if he'd had perspex."
He recalls having a budget of around £50,000. "Everything was from Wales. I got everything very cheap, I did a lot of bargaining, I'm not Welsh for nothing."
I look back on it with a lot of pride, pride for Wales and I'm very proud that I was involved in it
He got free slate from Dinorwic quarries: his godfather owned the firm.
Lord Snowdon is very proud of his work on the investiture and recalls relief on the day that, as he puts it, "it all went swimmingly" despite the deaths of two bombers near government buildings in Abergele two days before.
"People got worried about security and bombs and things like that there was no need.
"If there had been any terrorists they could have practised on me. I went around in an open Aston Martin or on my motorbike but nobody did actually have a shot.
"I think there were only two or three extremists. It didn't matter whether you were Welsh or not, this was bloody good for Wales and that was all there was to it."
He would like to see Prince Charles return to Caernarfon to commemorate the anniversary.
"He must come down again soon. I wanted him to come down this year but I think he said there won't be a celebration for 40 years, we'll leave it till 50, I'll be dead by then."
He bought six of the distinctive red chairs used for guests and still has them in his studio. He also still has the a distinctive olive green uniform he wore on the day, with Prince of Wales feathers on the collar of the tailcoat.
"It was simple, which carried through the whole thing," he says of a garment designed by Lord Plunkett, equerry to the Queen. "The front just had a zip, no decoration. It was very important not to look military".
The central dais was undercover, with everyone else open to the elements
"I used to wear it again afterwards for dinner sometimes, like at Balmoral when everyone dressed up in kilts and so on. I wore my investiture uniform." He adds, with a chuckle: "I'm not sure how well it went down."
Was the prince nervous? "He didn't show it. it must have been quite awesome at that age, don't you think? He did it beautifully.
"We did do a rehearsal in the garden at Buckingham Palace and we marked out a thing with string."
Lord Snowdon found it difficult to work with one official, the then Garter King of Arms - "a frightfully pompous idiot" - who designed the crown worn by the prince.
"His name was Sir Anthony Wagner, so you can imagine what we called him. I remember getting cross with him once or twice and I said to him, "Garter, darling, couldn't you be a little more elastic?"
Lord Snowdon took the risk of leaving the event open to the elements apart from the central dais.
'Moved on a bit'
"Somebody said to the Duke of Norfolk, "what do you do if it rains?" And he just said, "We all get bloody wet. It drizzled at one time but the only person that put on a macintosh was (Liberal leader) Jeremy Thorpe."
He has a simple message for opponents of the investiture: "Let them come forward and speak out, tell them to come around here and have a drink - I'll sort them out.
"I think the whole thing went swimmingly - anyone who didn't like it tell them to come and have a drink."
But he doubts whether a similar event will be held in future. "I don't know whether there'll ever be another one like it, there won't be one in my lifetime anyway, and I don't think there will be another one like it because it's quite a pageant isn't it?
"It was right for the day and the date but whether things have moved on a bit, I don't know."
Lord Snowdon has warm memories of 1969. "Nothing went wrong - Jeremy Thorpe and his macintosh was the only thing.
"I look back on it with a lot of pride, pride for Wales and I'm very proud that I was involved in it".
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