Terry Jones no longer recognises his 'Monty Python' co-stars.

The 76-year-old actor was diagnosed with Primary Progressive Aphasia, a form of frontotemporal dementia (FTD) that impairs the sufferer's ability to speak and communicate, in 2015 and his condition has deteriorated so badly, his co-star Terry Gilliam has revealed his pal has now ''moved into another world'' and he finds it ''difficult'' to see him now because he's unsure he knows who he is.

Gilliam told The Sun newspaper: ''I saw him a few months ago on Hampstead Heath. I find it difficult as he finds it hard to know who I am. This is a very dear close friend.

''I look in his eyes and I am not sure he recognises me. He walks along the Heath as Terry likes to get outside. Terry is in his own world is quite happy. I just miss him. It touches me.''

And the 77-year-old director particularly misses the arguments he used to have with his old friend.

He added: ''We argued our positions and fought for what we believed in. Terry has moved into another world. I miss arguing with Terry. He was always passionate about things. It is hard when you have spent your life arguing, fighting and being inspired by someone. When that character is not there anymore that is the sad thing. I hope he is content where he is that's all.''

Last April, Jones' daughter Sally insisted her dad was still aware of the people around him.

She said: ''Friends often ask: will he recognise me?

''I tell them: of course he will. It is his speech that has gone. In fact, he loves seeing friends. His only problem is that he no longer has the ability to tell them how pleased he is to see them.''

The surviving members of Monty Python - also comprised of John Cleese, Michael Palin and Eric Idle - reunited for 10 live shows at The O2 arena in London in 2014, and it was then that the rest of the group could see Jones was having problems performing.

Jones' family - including his partner Anna Soderstrom - went public with his condition in September 2016 to raise awareness of FTD, which, unlike Alzheimer's disease, does not result in a loss of reasoning.

However, decision-making and speech are affected and sufferers often seem less caring.