Surprise parties don’t always turn out enjoyably for that lucky person. It can be a bit of a freakout to find yourself surrounded by lots of family and friends without warning, even if you like or love them. So how would Megan react when her husband Tim Vincent-Smith fixed a mystery bus trip for her and their small children to celebrate her 40th birthday on the last Sunday in April?

As I pulled up just before Dean Bridge on the way into central Edinburgh, the four of them were rushing along to catch what Megan thought was going to be a regular Lothian service bus heading somewhere unknown.

Instead she got a 1962 red Routemaster with THE MEG BUS in the front ultimate destination box. Open-mouthed, she did a double take and they boarded – kids, cello, violin, picnic and all. (Tim is the creator of Pianodrome – motto: No piano is junk. No person is unmusical.)

Round the corner in Charlotte Square we picked up more passengers, including her parents. At York Place others got on and more again at Abbeyhill. Lots of food and drink came with them, then we set off – for Tyninghame beach. This glorious bit of coast east of Tantallon is where Tim and Meg were married.

Off the A198 and past the village we drove along Limetree Avenue – with everything coming into leaf – under a blue sky. We parked along the edge of a field and everyone got off, then Tim produced champagne. “Would you like some?,” Megan’s mother said to Sean the conductor and me. We had to decline. “Bad luck. That doesn’t seem fair.” Afterwards they all set off for the beach, reappearing about four hours later for a cheerful, and very musical, return journey.

The trip brought back memories for Meg’s father, who told me about his old daily Routemaster commute on the Number 9 from Barnes in south-west London to Aldwych. “I used to catch it at 6.30 in the morning, and often fell asleep. It was a clear run at that time of day, with hardly any traffic.” He was surprised to find out Routemasters never had a pre-selector gearbox, only automatic.

Back at the final drop-off, Charlotte Square, Tim said: “You should speak to Kay. She says it’s been one of the best days in her life.”

A smiling woman introduced herself. “I’m Kay, I’m a teacher. I’m quite old but I’m not going to say how old [that made me feel really old]. I’ve got kids and that was one of the best days in my life. You can put that on your website.

“It was an amazing atmosphere on board and the bus went at a perfect speed for the kids to play around,” Kay said. That’s the advantage of a top whack of 40mph. I’m not boasting but RM1353 goes a lot slower than that up steep hills with a decent load.

As for Megan, I’m pretty sure she enjoyed herself.