The familiar piano arrangement on Stevens’ recording
was performed by Rick Wakeman, a classically trained keyboardist with the English progressive rock band Yes.

In 2000, Wakeman released an instrumental version of “Morning Has Broken” on an album of the same title. That same year he gave an interview on BBC Radio 5 Live in which he said he had agreed to perform on the Cat Stevens track for £10 and was “shattered” to be omitted from the credits, adding that he never received the money either.

Apparently where “Morning Has Broken” is concerned, all Cat Stevens had was a hymn which lasted around 45 seconds. Producer Paul Samwell-Smith told him he could never put something like that on an album, that it needed at least to be three minutes in length. Prior to the actual recording Stevens heard Wakeman play something in the recording booth. It was a rough sketch of what would later become “Catherine Howard”. Stevens told Wakeman that he liked it and wanted something similar as the opening section, the closing section and, if possible, a middle section as well. Wakeman told Stevens he could not as it was his piece destined for a solo album, but
Stevens persuaded him and got him as far as adapting his own composition.[4] The familiar piano intro and general structure of the piece may be attributed to Stevens or to Wakeman.

http://en.wikipedia.org/wiki/Morning_Has_Broken