While he is now Covid-free and out of his induced coma, the effects of the virus have wreaked havoc on his body and he is in and out of consciousness.
Appearing on The One Show on Thursday to discuss a new documentary she has made about Derek’s Covid battle, Kate said: “Derek is an extreme case. What he had is what is called a prolonged disorder of consciousness which means that there is some reaction.
“It is not like the coma we see in movies where people are lying in a vegetative state. He can open his eyes and before Christmas there was a lot of progress with words and communication and things.
“But what I feel like is that I am on a lifeboat somehow and he is coming up and down. Sorry, this seems very figurative but that is how it feels.”
She continued: “You are on this precipice trying to hold on to him and there are moments when he bubbles up and you have some contact, predominantly at the moment on FaceTime because of the Covid restrictions.
“It feels like you are having to fill him with so much positivity because he is going to sink down. What you will see in the documentary is some of the better moments even though they are heartbreaking, I am afraid, where he comes up.
“Then you see what must be agony for him because he is somebody who, both in his time before I knew him when he was in politics and also since in all the work he has done in mental health, because that is his thing now, his brain has always been his best friend. He’s lived on his wit, and suddenly his brain – which also as we know controls the body – is no longer his friend and he’s fighting to get out.”
Kate added that however hard her experience had been during his illness, his would have been more difficult.
Earlier this week, the presenter told the Sunday Times Magazine that Derek’s condition has deteriorated “dramatically” since she was last able to visit him at Christmas.
There is no medical explanation for his regression, with Kate saying she suspects it is to do with a lack of contact.
She also said she is unsure if Derek will have “any kind of life again”.
The One Show airs nightly at 7pm on BBC One, while Kate Garraway: Finding Derek airs on Tuesday at 9pm on ITV.