It was supposed to be a low-key carol concert to bring a festive feel to a Staffordshire service station during the countdown to Christmas.

Then a swathe of stars strolled through the doors of the Norton Canes pit stop and pint-sized performer Lulu took the mic alongside part-time teacher Vie Watson.

The audience became a “sea of smartphones” with commuters clamouring for a glimpse of the impromptu duet – as Strictly Come Dancing heart-throb Harry Judd and fellow contestants Robbie Savage, Audley Harrison, Russell Grant and Edwina Currie joined the crowds.

The celebrities had been making their way up the M6 Toll to Blackpool for the weekend’s Strictly finale when they decided to take a short comfort break from the road, sparking “electric” scenes at the Roadchef services.

Mother-of-two Mrs Watson today told how seasoned entertainer Lulu asked her permission to share centre stage for a rousing rendition of Silent Night. The star then told fans: “She’s such a good singer, I couldn’t resist.”

The 42-year-old had been asked to appear at the services by husband and site director Peter. “He wanted to make sure there was a lovely Christmas atmosphere,” Mrs Watson, of Wolverhampton Road, Sedgley, said.

“I saw the group in the distance and recognised them. I wondered what they were doing here but I had a job to do and I carried on singing.

“They left but then returned en masse minutes later. They were all smiling and little Lulu came out of the crowd and asked if she would be able to sing Silent Night with me – I told her I was honoured to have been asked.”

Videos of the performance have become a YouTube hit and the singer, part of the choir at Calvary Church in Kingswinford, hopes it will heighten her profile. Mrs Watson, who has sung at footballers’ weddings and  Last Night of the Proms in Birmingham, said:  “I really hope opportunities come after this.”