A DOCTOR who was once too shy to sing anywhere but the shower has spoken of her joy and astonishment after a single she performed the opening solo on became this year's Christmas No 1.

Dr Zoe Davies said it had been "a massive surprise" when she learned the NHS charity single A Bridge Over You had been downloaded 127,000 times, topping efforts by Justin Bieber and X Factor winner Louisa Johnson.

Since winning the closest Christmas number one race since 2009 with physiotherapists, porters and nurses from Lewisham and Greenwich NHS Choir, the former Northallerton College pupil, said she had spent days celebrating with her family in Great Smeaton, near Darlington.

Dr Davies said: "Over the last week everything has gone a bit crazy and it feels like I fell asleep and am having a daydream.

"The single is a tribute to how much people in Britain value the NHS and so it's overwhelming to be one of the faces of that and to read how people have been moved by the single.

The 32-year-old medical registrar, who started singing in the choir three years ago and took part in the Gareth Malone BBC Two show Sing While You Work, said she had never thought she would be able to say she had performed on a chart-topping song.

She said: "I was really shy when I was at school and didn't have the confidence to sing in front of other people, so I would sing in the shower.

"I have had people messaging me saying 'I didn't know you could sing'."

The diabetes and endochrinology specialist said the song had been recorded in 2013, but had not been released as a single in November, as part of a campaign by junior doctors to make people aware of the pressure facing the NHS.

She said excitement had mounted at work when Justin Beiber urged his 72 million Twitter followers to buy the single, proceeds from which will be shared between charities including Carers UK and Mind.

Dr Davies said: "It was incredibly exciting recording it and the song, which is a mash-up of Simon and Garfunkel's Bridge Over Troubled Water and Coldplay's Fix You, fits in really well with what we do in the NHS.

"I hope what it can show is that Britain cares a lot about the NHS, that politicians should put it at the top of the agenda and that it gives the NHS a morale boost at a time of uncertainty about junior doctors' contracts and nurses' bursaries being taken away."