Ceratodon purpureus

Found on a thatched roof in Dorset this bryophyte I first thought was Dicranoweissia cirrata but it had dentate leaf tips. Because of this Bryoerythrophyllum recurvirostrum was considered but this species has papillose leaf cells and doesn't grow on thatched rooves. After consulting experts it was discovered that this species was indeed Ceratodon purpureus. The leaf state when dry prevented me from keying out correctly.

Ceratodon purpureus wet

Ceratodon purpureus dry

Ceratodon purpureus leaf

Ceratodon purpureus leaf section