I don't want to speak out of turn about Jarman's current 'powers' - I've only seen him the once, around 9-10 months ago - so I've got little to go on. But, someone said (maybe even here) that he's relatively frail these days.
When I saw him, he was very convincing musically, but he was battling physically with his tenor. His percussion was very musical, and he played some beautiful alto flute and melodica, but his tenor was very weak. [How hard on him anyway to have to follow the intensity of his peak!]. This may well have been hard for him, especially given that Mitchell was on absolutely incendiary form, and showed no signs of being anything other than completely on top of his game.
Don't know how, if at all, that bears on this, however!