Chris Tarrant's circled the globe exploring railways for his TV documentary series, Extreme Railways, but his verdict on our own rail system is damning.

"It's really depressing coming home after having travelled six times around the world in three and a half years filming rail systems, to find that of all the railways I've been to, it's ours which doesn't work," the 70-year-old presenter says sadly.

Tarrant, who first found fame in the Seventies hosting ITV children's show, Tiswas and presented game show, Who Wants To Be A Millionaire? from 1998 to 2014, faced his own personal challenge three years ago after he suffered a stroke while travelling from Bangkok to London following filming.

[Read more: Thinking about private health cover? Get a free, no obligation quote]

After collapsing at Heathrow, he was rushed to hospital for emergency surgery to remove a blood clot and spent months regaining total control of his speech and movement.

Pleased to be here

"I'm very pleased to be here because I had a big old scare. Even now I panic if I get a headache [a sudden severe headache with no known cause can be a warning sign of a stroke]. I think, 'Aargh, what's happening to my brain?'" he admits.

"The whole traumatic, shattering experience changed my outlook completely. Nowadays I believe in living for the day and am conscious of not wasting time.

“I no longer drink whisky, I exercise, take my medication and deliberately don't work as hard as before. I regularly make time to go away with my kids or to go fishing.

“Thankfully, doctors have told me as long as I don't backslide and start doing stupid things, then I should never have another stroke."

[Read more: 8 deadly myths you need to know about a stroke]

A complete recovery

Tarrant, who supports the Stroke Association, and hosted it's awards ceremony last year, says: "I know how lucky I was not just to come through it, but to completely recover.

“I was so terrified when I first got to hospital that although I hadn't slept for 36 hours, I refused to shut my eyes because I thought I wouldn't wake up again.

“If you've had a stroke you quite often have a second much worse one and I was determined to be able to alert the nurses if I did."

Tarrant lives in the Duchess of Cambridge's home village of Bucklebury, with his partner of 10 years, Jane Bird, 53, and has six children from his two marriages.

Jane has been wonderful

"Jane's been wonderful - constantly reassuring me throughout those first months by saying, 'You'll be fine, you're a tough old bugger!' I definitely wasn't an easy patient," he says with a smile.

‘Mentally tough’

"Luckily, I'm mentally very tough. In the past, I used that and work to help me get through hard times.

“When I was going through a very public divorce [from his second wife Ingrid] with press attention every minute of the day for months, I found going to work to host Who Wants To Be A Millionaire? was a wonderful distraction.

“I could think, 'No one can touch me here, this is my world', and it allowed me to forget about everything outside, just for a while.'"

Chris Tarrant

Nowadays, he's as disappointed with television as he is with UK railways. "I don't want to sound like a grumpy old man, but TV's declined hugely over the last 10 years," he declares.

"When the winner of I'm A Celebrity... isn't even a celebrity, but someone who just watches TV for a living [Scarlett Moffatt from Gogglebox won in 2016] and Britain's Got Talent's won by dogs twice, frankly you think the world's gone mad. I mean, God bless Ant and Dec because there aren't many other people of their stature around."

He has no such grumbles about his own life. "There were periods in my life when I couldn't imagine this happiness, but now I'm in a very good place. I don't need to work for the money, but want to do enough just to keep me mentally ticking over. I have my lady - we're incredibly happy together and have no plans to spoil that by marrying - and my army of wonderful kids. I can't ask for more."

The Railways That Built Britain With Chris Tarrant airs on Channel 5 on Mondays at 9pm.