Image copyright Official Chart Company Image caption Clean Bandit received a Christmas Number One award from the Official Chart Company

Pop group Clean Bandit have scored the Christmas number one single, with Rockabye.

The dance hit, about a single mother struggling to support her family, beat the competition to spend a seventh week at the top of the charts.

The band told the BBC they would celebrate with "some very large shots of Baileys".

Rag N Bone Man's blues ballad Human was at number two, 10,000 sales behind Clean Bandit's single.

One Direction star Louis Tomlinson was at number three with Just Hold On, a collaboration with US dance musician Steve Aoki.

Christmas top five singles Artist Title 1) Clean Bandit ft Anne Marie and Sean Paul Rockabye 2) Rag N Bone Man Human 3) Steve Aoki ft Louis Tomlinson Just Hold On 4) Little Mix Touch 5) Mariah Carey All I Want For Christmas Is You

Source: Official Charts Company

Rockabye first entered the charts nine weeks ago, and has racked up 589,000 combined chart sales to become one of the year's biggest hits.

The band told the BBC they had "no idea whatsoever" the song would become a smash.

"We were just putting out some music hoping for the best and it's just gone crazy," guitarist and writer Jack Patterson told BBC News.

"We did think about making a Christmas version but, there wasn't any need!" said cellist Grace Chatto.

It is the first song in chart history to become Christmas number one after such a long spell in pole position.

You have to go back to 1953 - a year after the singles chart launched - to find a comparison. That year, Frankie Laine's heartbreak ballad Answer Me became the festive chart-topper in its sixth week at number one.

Image copyright Getty Images Image caption Mariah Carey's All I Want For Christmas Is You is one of nine festive hits in this week's Top 40

More recently, the Christmas chart has been dominated by charity records, X Factor winners and "stunt" releases.

Clean Bandit are the first act to break this pattern since 2003, when Gary Jules' cover of Mad World claimed the number one spot.

Several charity singles were released this year, but failed to make much of an impact on the Top 40.

A tribute to Labour MP Jo Cox, who was murdered during the EU Referendum campaign this summer, made its debut at number 138.

The London Hospices Choir - a team of volunteers and staff from 18 hospices across London - reached 81 with their cover of Mike & The Mechanics' The Living Years.

And Inspiral Carpets fans sent the band's 1994 single Saturn 5 to number 48, in tribute to drummer Craig Gill, who died earlier this year.

Fans of Rangers football club fared better, pushing Glad All Over by The Dave Clark Five back into the charts at 31, as a "thank you" to striker Joe Garner, who joined the club from Preston this season.

But the rise of streaming has effectively killed the chances of such campaigns making a dent on the Top 40.

While, in the past, fans and sympathisers bought multiple copies of singles on CD and vinyl to support a cause, the charts now measure consumption of songs on streaming services. That gives popular tracks like Rockabye a distinct advantage.

In fact, if streaming data had been discounted, Rag N Bone Man would have been number one.

Image copyright Official Charts Image caption Michael Ball and Alfie Boe's Together tops the album chart

Top five albums Artist Title 1) Michael Ball and Alfie Boe Together 2) Little Mix Glory Days 3) Elvis Presley The Wonder of You 4) Rolling Stones Blue & Lonesome 5) Olly Murs 24 Hrs

Source: Official Charts Company

In the album chart, Michael Ball and Alfie Boe retained the number one spot with Together, their album of duets from the stage and screen.

The record has sold more than 446,000 copies since November - a quarter of them this week alone.

Only David Bowie's Blackstar has sold more copies in a single week this year, shifting over 146,000 copies in the days following his death in January.

Together is now the most successful album released this year (the other big-sellers, such as Adele's 25, were released in 2015).

"It's a dream come true," the duo said. "There's only one thing better than having a number one album and that's having a Christmas number one album.

"We hope we entertain you with the album for Christmas and lots of love to everyone."

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