Terry Jones co-directed Monty Python and the Holy Grail alongside Terry Gilliam, as well as solely directed Life of Brian and The Meaning of Life.
He also appeared in a number of the films during his time as a key member of the comedy troupe that includes actors John Cleese and Michael Palin.
The Welsh comedian, writer and actor has been diagnosed with a form of the disease called Primary Progressive Aphasia, it was announced today.
A representative for the 74-year-old said: “Terry has been diagnosed with Primary Progressive Aphasia, a variant of Frontotemporal Dementia.
“The illness affects his ability to communicate and he is no longer able to give interviews.”