Davis and Moore would for a time have a successful partnership working together not only for Marvel UK (including on Star Wars: The Empire Strikes Back) but also for 2000 AD on D.R. & Quinch (Davis also drew Harry Twenty on the High Rock for 2000 AD) and for Warrior magazine on Marvelman. The two later fell out as a result of creative differences and Moore's refusal to allow their Captain Britain series to be reprinted in America, denying Davis royalties as a result.
Following Moore's departure from Captain Britain, Davis briefly wrote the strip before collaborating on a further run with new writer Jamie Delano. In 1985, Davis successfully broke into the American market, working for DC Comics on Batman & the Outsiders and later Detective Comics (also on Batman). In 1987, he began working for Marvel Comics and, after collaborating with writer Chris Claremont on a couple of X-Men and New Mutants stories, became the original artist on Claremont's long-running series Excalibur, which teamed Captain Britain and his girlfriend Meggan up with a group of former X-Men. He also created the quirky superhero book Clan Destine for Marvel UK.
Davis has continued to work extensively for both DC and Marvel, on such characters as the X-Men, the Avengers, the Legion of Super-Heroes, the Fantastic Four, the Justice League of America, Wolverine and Killraven, as well as on a second series of Clan Destine. He frequently collaborates with inker Mark Farmer. He more recently worked on the Guardians of the Galaxy: Mother Entropy series, as well as The Infinity Entity, a limited series starring Thanos and Adam Warlock.
"Without question, Alan Davis stands in the top rank, among the very best. Story-telling, characterisation, draftsmanship, imagination — he not only excels in every category, he gets better as he goes along... On top of that, he's one of the nicest, most considerate of people to work with — and that's a rare charm in an industry where unbridled lunacy is the norm." (Chris Claremont, Captain Britain (trade paperback) Vol 1 1.)