I never thought I'd live to see the day that a Leonard Cohen song was in the chart - let alone the Christmas number one with two other versions at number 2 (Jeff Buckley) and 36 (Cohen himself).
This threesome, of course, sets off the question: "When was the last time three versions of the same song were in the chart at the same time?"
Having multiple versions of the same song in the charts was quite common in the 50s (and to a lesser extent in the early 60s), as the charts emerged out of the sheet music industry when the song was the important thing. Lots of singers tended to cover what were the most popular songs at the time.
Indeed, a quick flick through the Guinness Book of Hit Singles lists these songs which had three versions in the charts in the same year (I'd have to check if this was in the same week):
53 Broken Wings
55 Twenty tiny fingers
55 Blossom Fell
55 Hey there
55 Let me go lover
56 Cindy Oh Cindy
56 Green Door
56 No other love
56 Ballad of Davy Crokett
56 Woman in Love
57 Garden of Eden
57 Banana Boat Song
57 Around the world
58 Love me forever
60 Never on Sunday
On 20 June, 1955 Al Hibbler, The Les Baxter Orchestra, Jimmy Young and Liberace all scored a hit with Unchained Melody, with Young's version topping the chart.
In '64 Hello Dolly was in the charts with four versions in the top fifty, of which three versions were in the top thirty.
I can find two instances of five versions of the same song being in the charts in the same year: Suco Suco (that's ten "sucos") in 61 and Volare in 58.
But the biggest multiple versioned song which I can find occuring in the charts in the same year is Stranger in Paradaise from 1955 with six versions from Tony Bennett, Eddie Calvert, Don Cornell, Bing Crosby, the Four Aces and Tony Martin (mind you, one of those was an instrumental version as Eddie Calvert was a trumpeteer).
The most recent time I can find three versions of the same song appearing in the charts together was in September 1975 when "Out of Time" was a hit for Chris Farlowe (re-release), the Rolling Stones and Dan McCafferty. Mind you their top chart places were 44, 41 and 45 respectively so it is a fairly unconvincing occurence of the multiple versioned hit.
So, I think you need to go back to Hello Dolly in 1964 for the last time that three versions of the same song were in the top forty together, as the three versions of Hallelujah are today. Those were, by the way, versions by Frankie Vaughan, Kenny Ball and his jazzmen (an instrumental, I'd guess) and Louise Armstrong.
I am now off to see what places they had in the chart at the same time...and I'll also check that there haven't been any threesomes since 1979 when my battle scarred version of the Guinness Book (2nd Edition) was published. The BBC reckon that Unchained Melody in 1955 was the last time that three or more versions of the same song were in the chart at the same time. They are probably right. I never am (right).
The Official Charts Company said the only other time the (same song at numbers one and two) scenario occurred was in January 1957 when Tommy Steele and Guy Mitchell held the top two places with Singin' The Blues.