Alan Titchmarsh, the celebrity gardener, veteran broadcaster and now officially a national treasure, summed it up perfectly.

“It’s all a bit surreal,” he said.

I could see why. We were sitting in an open top double decker – one of seven buses that where taking part in the Platinum Jubilee Pageant. Each bus represented a decade during the Queen’s reign, from the 50s through to the noughties.

We were on the 60s bus and the seats on the top deck were occupied by some of the best-known and most loved British celebrities.

At the front of the bus I saw Valerie Singleton – former presenter of the iconic children’s programme Blue Peter – taking a selfie with Basil Brush.

On the 50s bus parked next to us, pop legend Sir Cliff Richard was miming along to one of his hits, blaring out from a loudspeaker. Standing next to him was the former boxer, Chris Eubank. And not far from them both, dancer Wayne Sleep blew kisses at the stars on my vehicle.

That is what Alan Titchmarsh meant by “surreal”.

It seemed that anyone who has ever been anyone on stage, screen, in a stadium or a recording studio was there.

TV presenter Chris Tarrant, on the 70s bus just behind us, winked at me and asked if I was OK.

Would he take “yes” as my final answer or could I phone a friend?

Celebrities really like other celebrities, it seems. They can’t possibly all know each other. But that is exactly how they were greeting one another. Lots of hugs, air kisses and selfies. LOTS of selfies.

Many of my Sky colleagues would be able to name most if not all of the stars on the buses, but this was a real test of my A, B, and C-list knowledge.

It was not a problem for the adoring crowds lining the streets below, however.

As the celebrities let their hair and their guards down the cheering throng went into a frenzy.

It is not every day that you see the actor Rudolph Walker and broadcasters Kate Garraway and Anthea Turner dancing like nobody was watching. But they were.

The veteran broadcaster and DJ Tony Blackburn could not stop smiling. I asked him who would be on a playlist for the Queen. “Diana Ross and lots of Motown,” he said without hesitating.

The concert at the gates of the palace on Saturday night brought together some of the biggest names in the world of music. I heard a commentator say that only the Queen could have drawn them to the same place at the same time.

The same is true of the People’s Pageant. The former decathlete Daley Thompson next to singer Tony Hadley? Pure gold.

And each one of these celebrities enjoying every second, too.

They knew this was a once in a lifetime opportunity to enjoy a celebration like no other – almost all of them describing themselves as “privileged” to be able to ride on these buses on this very special day.

It was a random, eclectic, crazy mix. Eccentric in a uniquely British way. An experience nobody will forget.