A true romantic has stunned his Harry Potter-mad girlfriend with a magical proposal - popping the question on a personalised number plate aboard the Hogwarts Express.

Sophie Irwin was already enjoying a dream day out to see the Jacobite Steam train at the famous Glenfinnan Viaduct in the Highlands.

But the 31-year-old couldn't believe her eyes when she saw the train, featured in the Harry Potter films, cross the viaduct with a sign saying 'Sophie Marry Me' on the front.

When she turned to boyfriend Graeme Tait he was on one knee in the mud asking her to marry him.

Graeme, a radiographer, had planned the magical moment by asking the train company to replace the usual Jacobite nameplate with his personalised message.

The 31-year-old, from Berwickshire, had secretly mapped out the whole proposal before the couple, who now live in London, set off on holiday in Scotland.

He had picked out a perfect spot for the pair to watch the train go by and made sure it would pass slowly enough for Sophie to read the sign.

Sophie, an anaesthetist, said: "We were on a two week touring holiday around Scotland in October and had planned to take a trip on the steam train while we were in Fort William.

"Graeme had suggested that the day before getting on the train we should go watch it go across the viaduct.

"I am a huge Harry Potter fan and Graeme knows I have always loved the romance of travelling by steam after visiting railways in England.

"Graeme said he knew the best spot for watching the train go across the viaduct, so we got there early and picked a spot.

"He was acting very odd, a bit sheepish, and he just wasn't himself.

"He kept asking me what I thought it would say on the front of the train and I said I knew it would read The Jacobite.

"But he was trying to convince me it would say The Hogwarts Express.

"The train signalled it's arrival on the viaduct by sounding its horn and he said again 'what do you think it's going to say on it'.

"I was videoing it coming across and I realised it was going very slow, and then I saw my name and when I turned around Graeme was on one knee in the mud."

Graeme had even arranged for an announcement be made to passengers on board the train, letting them know to look out for the proposal as they passed by.

"The passengers on the train were hanging out the windows shouting congratulations", said Sophie.

"I just couldn't believe it - I wasn't expecting it at all.

"The next day we went on our train trip and we were presented with our sign, which Graeme had specially commissioned from a company in Yorkshire."

The famous viaduct carries the railway to Glenfinnan Station across a 1,000 ft span, 100 ft above the ground.

The Jacobite steam train runs to Fort William and Mallaig in summer and was featured as the Hogwarts Express in J.K Rowlings Harry Potter films.

The happy couple has already set a date for their big day in August next year, and Sophie has plans to make sure her love of Harry Potter is included.

She said: "I have had a Hornby replica of the Jacobite train made to go round the bottom of our wedding cake."

But two months on the couple are still trying to solve one mystery from that special day.

Sophie explained: "Prior to boarding the train, we were presented with some photos.

"There had been a professional photographer on the line and he had noticed the special head board.

"He managed to take some spectacular photos of the train on the viaduct and going along the line.

"He printed them out for us and staff at the station gave us some printed copies after he handed them in.

"He left his name, Bernie, and a contact number but unfortunately the number doesn't work.

"We really want to get in touch with him to thank him and get digital copies of the pictures.

"So if anyone can help us track him it would be greatly appreciated."