Mark Ronson's Uptown Funk might have been released nearly two months before 2015 began but it has still clinched the title of biggest-selling song of last year.
The dancefloor-filler, which featured Bruno Mars on vocals, notched up a combined sales and streaming total of 1.76 million, according to the bean counters at the Official Charts Company - and that excludes the 490,000 it sold on its November 2014 release.
With all twelve months to rack up sales, Ronson had a clear advantage in the list of top-selling songs of 2015, and honourable mentions must go to Adele's Hello and Justin Bieber's Sorry, which took sixth and tenth place respectively despite their late October release.
Summer's smash hit Cheerleader (Felix Jaehn Remix) by OMI, which crept its way up from number 96 in the charts in January to spend four weeks at number one four months later, comes in second with 1.52 million sales.
Rounding off the top three is another slow climber: Hozier's stirring Take Me To Church spent 20 weeks climbing the top 40 but missed out on the top spot, peaking at two for four consecutive weeks and amassing combined sales of 1.25 million.
Pipping Hozier to number one for three of those weeks was Ellie Goulding's Love Me Like You Do. The power ballad featured on the 50 Shades of Grey soundtrack and soared to chart victory back in February; by the end of 2015, it had racked in 1.19 million combined sales.
Wiz Khalifa's Fast & Furious 7 tribute to late actor Paul Walker rounds off the top five. See You Again finished close behind Goulding with 1.17 million sales.
Putting into perspective Ronson's achievement, Adele's first track Hello from third album 25 became the fastest-selling single of the year and the biggest number one in three years, shifting 333,000 copies in its first week in October, and helping her to earn sixth place in the list with 1.12 million combined sales.
Hello also smashed Bieber's streaming record of 3.2 million plays for What Do You Mean? when it achieved 7.32 million streams in just one week.
Bieber can console himself with two tracks in the top 10: What Do You Mean? in ninth place with 988,000 sales, and Sorry at 10 with 934,000, both long-term chart toppers.
Lean On by Major Lazer featuring MO & DJ Snake came seventh while James Bay's Hold Back the River, the second single from his debut album, came in eighth.
Other notable mentions among the top 40 biggest-sellers of 2015 are Ed Sheeran's Thinking Out Loud at 12 and three spots for Jess Glynne and an equal count for US R'n'B star The Weeknd.