Andrew Flintoff's breath could kill a man from 100 yards away. At least, that's what he warns me when we sit down in the deserted restaurant of a hotel in Elstree. "I've been on the caveman diet," he explains. "Steak for breakfast, two chicken fillets for lunch, grilled fish and vegetables in the evening and 13 almonds to snack on throughout the day. I've lost around 18kg now, but my God it makes your breath stink. I've got a huge tub of emergency chewing gum in my car, so tell me if it gets too bad."
Halitosis aside, the former England cricket captain turned TV personality is in impressive shape. Flintoff has always been a good-looking lad, but now that his Northern bulk has dwindled a few sizes his appearance reduces the hotel receptionist to schoolgirl vapours.
His drastic downsizing has not been driven by vanity. Rather, over the past four months the 34 year-old has been training to become a professional heavyweight boxer. Under Barry McGuigan and his son Shane's intensive tutelage, Flintoff has spent up to eight hours a day in the ring preparing for a fight - going out live on Sky - in Manchester Arena on November 30.
"It's the hardest thing I've ever done," he says, his speech blurred by a fat lip and crushed nasal cavity. "With the cricket I knew what I was doing - to a degree," he grins. "But this is so new that I don't know where I am with it. I'm used to playing in pain, but this is self-inflicted."
The boxing has been such a huge commitment, says Flintoff, that even though he's been able to spend more time with his 34-year-old wife, Rachel, and three children, Holly, eight, Corey, six and Rocky, four, he feels a bit distanced from them. "I was never like that with the cricket. I could switch off. But last night I was so tired that I nearly ground to a halt."
Ever since Flintoff was forced to retire in September 2010 because of a knee injury, he's been seeking new challenges. Life isn't easy for ex-cricketers: unable to replicate the highs of the pitch, a larger percentage of them slide into depression than any other professional British sportsmen.
Flintoff - along with team members Marcus Trescothick and Tim Ambrose - contributed to those statistics when he admitted to suffering from a bout of depression in 2006, in the wake of England's Ashes triumph. This came as a big surprise to his fans. Gregarious by nature, Flintoff (whose nickname is Freddie because he reminds people of the Flintstone character) won the hearts of the nation when he was discovered drunk in a pedalo in St Lucia during England's World Cup campaign in 2007.
A prankster and bon viveur, he was the guy fans wanted to go drinking with. Nobody would have imagined that the 6ft 4in Lancastrian, who always looked like he was holding back laughter in post-match interviews, had an introspective side. The BBC documentary on depression that he presented last year may have proved cathartic, but it failed to provide any answers.
"I still don't know why cricket has a higher depression rate than the others," he shrugs. "Maybe you've got a lot of time to think because you're stood in a field. Or maybe it's because when you leave, you're leaving the safety of a team. You're never prepared for the end of a career. And it's not like with football, where you've banked all this money - you've got to go and find a job and you've not got anything you can do. I'll see cricketers playing until their mid-thirties and I'll fear for them because they're going to be scrabbling around afterwards doing speaking engagements to support their family."
Flintoff has been luckier than most. During the past two years, he's developed a credible career as the Gary Lineker of cricket. A TV presenter and radio personality, he's team captain on James Corden's Sky sports panel show, A League of Their Own, and has fronted a handful of documentaries.
Even so, sports writers and TV critics have been scathing about this latest venture. "I don't know why there's been quite a lot of negative stuff," he says good-naturedly. "But if that's before I even get in the ring, hopefully it can only get better. All I know is that training opposite Barry McGuigan wasn't an opportunity I was going to turn down. What's really surprised me, since it's been announced that I'm doing this, is how many people want to punch me," he laughs. "An offer comes in on Twitter every two minutes."
I wonder if the boxing, like the depression, is proof of Flintoff's hidden dark side, but he assures me that he's neither "angry" nor "confrontational" - and has never hit anyone outside the ring. "I never got a thrill from that kind of thing. The school I went to was quite rough so I just kept my head down."
He grew up in Preston with a cricket-mad plumber father and was forced to play football at school - and hated it. "Cricket was a posh kid's sport but I was always dreadful at football. Dad was never pushy - but the cricket was always there." He got to play his first game when he was six years old and the local under-14s were short. "I was wearing a Manchester United track suit (a hand-me-down from the family across the road who had six children) and I was frightened to death."
After joining Dutton Forshaw cricket club, Flintoff made his debut for Lancashire in 1995 and his test debut for England against South Africa three years later. He remembers his first meeting with West Indian cricket legend Sir Vivian Richards. "I was 22 and Viv started talking to me about my batting in the bar after a game. I couldn't believe that he knew who I was. I've only ever been star-struck by cricketers because I've never aspired to be anything else."
When Flintoff talks about cricket, the levity in his expression drains away and he starts pushing the salad around his plate. "I'd swap everything I have now to play cricket again," he says eventually, looking up at me. If he could relive a single day of his career, which one would it be? "I'd like my last one again," he replies after a moment's thought. Not the day they won the Ashes? "No," he chuckles, "I don't think I could do that night again - I've not got it in me. But that last day… it went by so quickly. I don't remember much about it except getting pretty emotional with my family after the game."
The dressing room atmosphere has changed, over the years, he adds with a shake of the head. "My first three years at Lancashire… well, things weren't as professional as they are now. There were pints after play every night and I'd even have a cigarette from time to time. But now it's all ice-packs and protein shakes. We've got to be careful that cricket doesn't get like football."
What did it feel like to play for his country? "It made you feel taller, stronger somehow," he smiles. "You get this hit of energy, like you're a kid at Christmas and you're so excited about the next morning that in bed your legs can't stop running. It was an amazing feeling. And that's one of the things I miss most."
The boxing may be a fun diversion - just the challenge Flintoff needed to reboot his confidence - but he could now earn millions as a specialist batsman in 20/20 cricket. "Part of me still thinks I could play," he nods. "I haven't been as fit as this in a long time… The other day they put an old game on telly; I was playing in it but I didn't at any point think it was me. It was bizarre - there was this complete detachment there, like I was watching someone else. I'd reached a point where cricket seemed so long ago. But now that I'm fit again…" He pauses.
"Well, you start thinking: could I?"
From Lord's to the Ring starts on Sky 1 HD on November 22. To buy tickets to see Freddie fight at Manchester Arena on November 30 call 0844 847 8000