Pop star Ellie Goulding has scored the final number one of the decade, with her version of Joni Mitchell's River.
Her track dethrones LadBaby's I Love Sausage Rolls, which plummets to number 57 after just one week on the chart.
River is Goulding's third number one, following 2013's Burn and 2015's Love Me Like You Do.
She managed the achievement despite the song being an Amazon exclusive, meaning it was unavailable on Spotify, Apple Music and other streaming services.
However, fans could stream the song on YouTube, where it was accompanied by a video highlighting the problem of plastic pollution.
The clip, directed by David Soutar, sees Goulding and her friends gathering litter and discarded plastic on the beaches of Dungeness, and using it to make a zero-waste Christmas tree.
Shooting the video was "a timely reminder that every single piece of plastic ever made is still on this planet," the star said in a statement.
"It's a material that will last for hundreds of years so we need to have a plan. We wanted to show something different and to incorporate a different type of Christmas message while creating something reusable and beautiful."
The track scored 78,000 chart sales. The rest of the singles chart was dominated by Christmas songs, with 29 festive hits appearing in the Top 40.
Mariah Carey's All I Want For Christmas Is You led the chasing pack at number two, with Wham's Last Christmas at three. Both songs were streamed more than 1.5m times on Spotify on Christmas Day alone.
Furthermore, the latter track, featuring the vocals of the late George Michael and Andrew Ridgeley, failed to reach even number two despite having set a new UK chart record for the most number of streams in one week - overtaking Ariana Grande's 7 Rings - with a massive 17.1 million plays.
In the album chart, Rod Stewart's You're In My Heart held on to the top spot for a third week.
The record, which features new orchestral arrangements of hits like Maggie May and Stay With Me, is the star's 10th number one.
Michael Buble's Christmas album was at number two - its highest chart placing since it was first released in 2011 - followed by Lewis Capaldi's platinum-selling Divinely Uninspired To A Hellish Extent at three.
And Lana Del Rey's fifth album, Norman Rockwell, rebounded 45 places to number 32, after topping numerous "best of 2019" lists in the run-up to Christmas.