TSR UK was the British division of TSR and the starting place for many of the UK RPG luminaries. Imagine was a magazine in the same vein as Dragon and Dungeon magazines, but publishing all original content from mostly UK writers. A lot of the same people contributed to the fanzine Imazine ("I'm a zine"), which provided an outlet for much of the gossip from TSR UK.
From Wikipedia; "Imagine Magazine was a monthly magazine dedicated to the first edition Advanced Dungeons and Dragons and Dungeons and Dragons role playing game systems published by TSR UK Limited between April 1983 and October 1985. The print run lasted for 31 issues, (30 monthly issues and one special edition) before its cancellation.
Don Turnbull was cited as Publisher and Paul Cockburn as Assistant Editor throughout the majority of the lifetime of the publication.
Imagine Magazine was responsible for several creative spin-offs, notably the Pelinore gaming world. The magazine also featured the classic adventure game comic "The Sword of Alabron" in issues 1 to 16. This was briefly revived as a second story arc titled "Auchter's Axe" in issues 29 to 30 prior to the magazine's cancellation.
Neil Gaiman wrote film reviews for several issues of Imagine Magazine in the early part of his career, taking over from Colin Greenland, and had his first short story "Featherquest" published here in May 1984. Gaiman's "How to Sell the Ponti Bridge", reprinted for the first time in M is for Magic was also first published here in March 1985.
When some disgruntled TSR UK staffers left, they started GameMaster Publications, to attempt to preserve the experience of Imagine, which included some popular features such as Pelinore. The magazine also ran various articles containing details on Imagine's closure, and criticized Gary Gygax, and TSR negatively."