I had a similar experience in Brighton in February. Here's what I posted to the uk.music.folk newsgroup:

"How very, very sad. Went to see Davey Graham last night in Brighton. But he's really not up to the job, I'm afraid. There were spells during the performance where you could see and even hear some of the spark that was once there, but by and large it was an uncomfortable evening for the audience who were shocked and embarrassed but also, incredibly, very warm and supportive throughout. "

and:

"If he came to pretty much any club I've ever been to unannounced and unrecognised, they wouldn't mind too much if he came back or not. By no means the worst floor spot I've ever seen; but on any given night he'd be there or there about."

and here's what his agent replied:

"The morning of the Brighton concert was the height of the snow in Oxfordshire. I had to have the car towed for three miles to get to a passable main road. Davy had a streaming head cold which had affected his hearing slightly. We were trying a new small bodied Martin OM-31 that wasn't quite set up to our high standards.
The seating arrangement seemed to be a bit weird. Looking sideways. We are going to just do small theatres in the sense of tiered seating
from now on.
Davy played well. Not like a boxer, more like an older bull-fighter.
Attempting dazzling moves.
He is currently staying in Gloucestershire getting things together for the album, and appreciates everyone's support. The gig the week after in Exeter was much better. Its a long road. Each performance is
unique. There is some more work needed to fix some problems. Its
personal to Davy and I don't want to have to spell that out too much.
We are doing more gigs now and just one so-so performance gets a
dissproprtionate ammount of attention. It is only a hall, and a
gathering, and an idea really. Its nice when the audience mixes and
talks to one another. London doesn't suit him and never has, but I can only do what I can do.
Mark Pavey"

Draw whatever conclusions you like.

--
Hamish