IN A LIFETIME is a career-spanning anthology containing tracks from Clannad’s 50-year recording career, compiled in conjunction with Clannad band members. The albums contains two new tracks, "A Celtic Dream" and "Who Knows (Where the Time Goes)", the first recorded by the group since the passing of member Padraig Duggan.

The cover art features the last four remaining members of Clannad sitting on a currach on the Clady River in their hometown of Gaoth Dobhair, County Donegal.

After the first evening’s recording session was completed an electrical storm raged throughout the night which inspired many of the artists to bring extra lyrics and ideas for the track to the following day’s session, with Pol Brennan explaining later that he had stayed up much of the night writing. The single was released on four formats, which included a picture disc version of the 7" vinyl release. This is available as a 2CD set, a 2LP coloured vinyl and a sizeable super deluxe edition box set that features four CDs, three vinyl LPs, a seven-inch record, a book, postcards and poster. Clannad had already written most of the lyrics for the song and recorded a backing track when the group asked Bono of U2 if he would collaborate with them on the recording, the first time the group had allowed an outside artist to join them in recording one of their tracks.

The B-side of the single included the track " Something to Believe In", a collaboration with American musician Bruce Hornsby, taken from the 1987 Clannad album Sirius. The recording session, as Moya Brennan remembers, was “one of the most remarkable things I’ve ever seen in a studio.Released on 3 April 2020, the album was to coincide with the band's 50th anniversary as a group and they subsequently embarked on a world tour. Next month, BMG will release In A Lifetime a new Clannad anthology available across various physical formats. The single was re-released in 1989 with a change of artwork on the cover and a different B Side ("Something To Believe In (edit)").