There are two guitars that hold a very special place in John Illsley’s heart.

One is the 1961 Fender Jazz that he played on stages around the world as bassist for Dire Straits, strumming out the chords for hits such as Telegraph Road and Sultans of Swing.

“The strings haven’t been changed for 25 years and it’s really beaten up and nothing sounds like it,“ he says lovingly.

The other is the 1963 Gibson J50 he took into hospital when he was being treated for chronic lymphocytic leukaemia and wrote his new album Testing the Water on.

“I think music was quite a good way of coming to terms with it,“ he says of his battle with the disease, which he kept secret for 15 years.

“It’s quite handy being a songwriter. Other people do something else to deal with the anxiety, but what I found was when I began to write about it, it helped me understand it.“

He adds: “I played every day and wrote one complete song in hospital and sketches for two others. It was a fairly reflective time really. Railway Tracks came out of that and if you listen to the lyrics it’s painfully obvious what it’s about.“ (Life doesn’t run on railway tracks, It twists and turns; it’s not white or black).

Speaking to the 65-year-old just hours before his tour starts he is full of excitement and decibes himself as “fit as a flea“.

But the father-of-four admits it was a “bombshell“ when he was diagnosed in 1999 and, not wanting to continually be talking about it, he made the decision not to tell anyone apart from a handful of those closest to him, including Straits singer Mark Knopfler.

“He was silent for a minute and then said “bloody hell mate. What’s going on?’,“ says John recalling the moment.

“He was wonderfully supportive as usual and I knew I could trust him to respect my wishes to keep it quiet.“ John only decided to speak out about his ordeal now in order to thank his sister Pat, who donated her stem cells, and to raise awareness for Anthony Nolan, the UK’s blood cancer charity and bone marrow register.

“I was very lucky having a match with my sister, so I kind of owe her my life,“says John, admitting they both shed a tear when they were told she was a match.

“But if I hadn’t had a stem cell transplant from her I would have gone to Anthony Nolan and one of the reasons I came clean about it was I wanted to make people donate.

“My eldest daughter is on it and my daughter who’s just turned 16 will go into it and my son who’s 18 will go onto it. You literally just spit into a bag and send it in, I’m not kidding, and then you are on the list.“

John, who started playing guitar as a teen on a Rosetti Lucky 7 bought for £10 and learned bass on an instrument nicknamed The Spade made by his brother in woodwork lessons, formed Dire Straits in 1977 with Mark Knopfler, David Knopfler and Pick Withers and went on to live the high life all over the globe as they became one of the most successful rock bands of all time.

But since they broke up in 1995, John has lived a fairly healthy life in the New Forest with second wife Stephanie. He says it left him “perplexed“ when doctors gave him ten years to live when he was just 50 and he was determined to prove them wrong.

“I’m an optimist, so I had absolutely no intention of not finding a match. I would have gone anywhere.

“I have got two young kids and have a wonderful life and wasn’t going to lie down and put my legs in the air. I’m not that kind of person.“ John carried on working through his illness, which left him so weak he could barely walk at times, but also spent a lot of time on his other passion – painting, and is planning an exhibition for next year.

His first gig back, 18 months ago at the Half Moon in Putney, was attended by a group of nurses who treated him, and was recorded and made into an album, Live in London, which is not yet released but which fans will be able to buy exclusively at the Watford gig.

But first John, who used to own a driving range in Borehamwood, so “knows Watford well“, is keen to share the music from Testing the Water, which he worked on with Mark and Straits keyboardist Guy Fletcher as well as some old classics such as Romeo and Juliet.

“I’m still able to get up there and lay it down fairly well so I’m happy about that.“ Although he would “love it to happen“ a Straits reunion is highly unlikely but in the meantime John is happy to carry on playing the music that made them famous.

“When I play at Watford they will hear eight or nine Dire Straits songs and I think we do them pretty well.

“Now that I’m doing all the singing in the front there it’s not quite as relaxing as standing on the side and watching Mark do it.

“So the load is somewhat falling on me a lot more and I have to say I’m enjoying that, which I never thought I would.“ So is it fair to say his illness given him a new perspective on life?

“It gives even more reason to go out and enjoy yourself. When you have been close to meeting your maker, that is a bit dramatic, when you are quite seriously ill and they take you down to zero and build you back up again, it’s quite an interesting mental thing to go through.

“It makes you think quite seriously about things. I know that’s quite predictable, but it’s important to pick yourself up and carry on.“

John Illsley and band will be playing music from Testing the Water and the music of Dire Straits at Watford Colosseum on Sunday, October 5 from 8pm. Details: 0845 075 3993, watfordcolosseum.co.uk