Lord Falconer lost five stone, going from 16st 6lb to 11st 5lb in two years

At Lord Falconer’s house in Islington, North London, there are two sets of clothes. One for the 16-and-a-half stone peer of 2012, and another for the new ultra-slimline version, currently 11st 5lb — dipping on occasion to 11st 2lb.

‘I’ve kept most of my old clothes,’ says Falconer, 62. ‘I assumed that the moment I bought new clothes, I’d put weight on again. So for a while, I was lost in clothes that were too big. The effect of buying new clothes was to make me look even thinner.’

And boy, does he look thin!

Lord Falconer lost five stone in two years after drastically changing his diet and taking up regular exercise

The last time I saw Charlie Falconer, he was Lord Chancellor in the Labour government of his friend and former flatmate Tony Blair. He was a widescreen picture of tubby jolliness.

Unlike the rest of the joyless New Labour government, Lord Falconer was a big luncher — and keen on a drink at lunch and in the evening.

No longer. On New Year’s Eve 2012, he gave up drinking. He then went on the 5:2 diet, where you fast for two days a week and eat normally for the rest of the time.

‘That didn’t work that well — I couldn’t show restraint,’ he says. ‘Not eating a meal at all, I find easier than having a small meal. Once I’m eating, I want to eat more.’

And so he turned to having just one meal in the evening, and staved off the hunger pangs during the rest of the day by eating endless apples and knocking back nine Diet Cokes.

In the meeting room of the U.S. law firm in Central London where he works as a partner, four cans of Diet Coke sit on the drinks tray next to the bottles of sparkling water, and he sips from a can while we chat.

Falconer — who last exercised properly at school 44 years ago — has also taken up jogging five miles a day, and has even given up tea and coffee.

He looks a new man — and, ever since his dramatic weight loss was in photographs this week, he has been praised wherever he’s gone.

‘I realised something unusual had happened when driving in my car,’ he says. ‘The second item on the Heart FM news broadcast said “Lord Falconer had lost 5 st.” It struck me as bizarre — the idea that ebola didn’t get a mention.

‘Earlier in the day, a lady with a dog, who I’d never met before, stopped me and said, “Go for it, Charlie. Keep on losing weight!”’

Fuller figure: Lord Falconer now only eats apples until dinner, drinking up to nine cans of Diet Coke a day to stave off hunger

Indeed, it’s been one of the strangest weeks of his career, which has included heading the country’s judiciary as Lord Chancellor, and being one of the ministers responsible for the Millennium Dome. Yet for the past 20 years, he admits he was rarely recognised.

‘The public showed no interest in issues like the precise composition of the Judicial Appointments Commission,’ he says wryly. ‘For the very first time, with the exception of the Dome — when I wasn’t altogether regarded as a success — there has been a quite unexpected connection with people.’

And he’s delighted by it. ‘It’s much bigger news than when I was Lord Chancellor. There’s been great interest and enthusiasm.’

Many old friends have also been in touch to congratulate him — including Tony Blair, although Falconer would prefer to keep the details of their conversation private. Surely the next step is a diet book, like the one Lord (Nigel) Lawson, former Tory Chancellor of the Exchequer, wrote after his dramatic weight loss.

‘Nobody has asked me to write a book,’ Falconer says. ‘It had never occurred to me that people would want a book.’

But he welcomes the publicity because, until now, many people thought illness had led to his weight loss. Among them was Lord Butler, the former Cabinet Secretary, who asked Lord Falconer’s wife: ‘What’s wrong with Charlie?’

At the time, Falconer was campaigning for the controversial Assisted Dying Bill, which would allow doctors to prescribe a lethal dose to terminally-ill patients, and which reaches committee stage in the Lords next week.

When Marianna Falconer, a QC, explained to Butler about her husband’s diet, he responded like a true politician: ‘Well, please don’t tell anyone because it will increase the sympathy vote on the Assisted Dying Bill. They’ll think, poor Charlie, we’d better vote for his Bill because he’s dying anyway…’ Falconer is sanguine. ‘I didn’t mind Robin Butler saying that — he’s a very straightforward guy,’ he says. ‘And now a lot of people who thought I was suffering from a wasting disease of some sort have come up to me to congratulate me.

‘Some people said before, “How marvellous you look.” Others were clearly thinking, “You look terrible; what’s happened to you?”’

Falconer wasn’t in poor health when he began the diet, either — but his weight was on his mind.

‘There was a point when I was aware I was very, very fat,’ he says. ‘There are so many not entirely inaccurate photographs of me as very out of condition.

‘It’s not a trick of photography — you can see about 43 chins from some angles.’

He felt, he says, less fat than he actually was. ‘I never felt plump, even though I knew I was. If you look at holiday snaps, I looked even fatter, sunbathing.

‘Then there was the health aspect. The cholesterol levels and blood pressure levels were fine but, at the age of 60, diabetes, heart disease and stroke are all going to be made worse by being fat. I thought at the end of 2012 that, if I didn’t do anything about it now, I’d never do anything about it.’

Still, being fat had, if anything, been something of a political advantage for Falconer.

Fuller to thinner: Lord Falconer runs five miles a day to keep fit, but says he is still partial to chocolate after eating dinner

‘We live in a time where what you look like physically is very important,’ he says. ‘Peter Mandelson was the slim, ascetic individual.

‘For me, being a fat and genial politician went together. It helped hugely.’

‘Cassius is a lean and hungry man,’ says Falconer, quoting Shakespeare’s Julius Caesar. ‘And jolly Charlie Falconer has turned out to be a lean and hungry man — not so hungry even.’

Falconer didn’t follow any book or take advice from a particular doctor, improvising the Apple and Diet Coke Diet himself.

‘To begin with, I ate what I wanted in the evening,’ he says. ‘It started off being roast beef and Yorkshire pudding. But then it changed. I became quite ambitious about the weight loss. It’s now chicken and fish and jacket potatoes and salad.’

But he does, he says, allow himself some pudding: ‘I’ll eat chocolate at the end of it.’ He doesn’t pretend it’s easy, though.

‘I still get very hungry and that’s why the Diet Coke and apples came in. They are an extensive distraction activity. It doesn’t remove the hunger.’

He says there was no pressure from his wife and four children to go on a diet. Quite the opposite, in fact. ‘They thought I went at this too hard,’ he says. ‘They thought I’d got thin enough.

‘They’d had enough of the scale of the physical change. People don’t like that much change around them. That’s not what they think now.’

Several commentators have suggested that it’s a particular sort of male iron will that leads to such dramatic and successful dieting, but Falconer doesn’t agree. ‘I tried and failed many times before. It’s not a male thing — there are lots of women who’ve lost more weight.’

For him, the secret was becoming aware of how his eating habits affected his weight.

‘The regime was a response to the way the scales operated. I’d weigh myself twice a day, making a connection between what I was eating and my weight.

‘That led me to believe after two weeks I could control my weight. It was incredibly encouraging to see I could lose 2-3 lb a week.’

The change in his body has transformed his mood, too.

‘I feel much brighter — sunnier, even though I wasn’t gloomy before,’ he says. ‘And I feel much brighter in the sense of being sharper.

‘I can absorb more information. I can have tricky discussions in the middle of the afternoon. Not carrying around 5 ½ st means I’m better at thinking.’

Yet isn’t life, well, a bit more boring?

‘I’ve got my Diet Coke to look forward to! I was a pretty consistent drinker,’ he admits.

‘I would drink at lunch time; I would drink pretty well every evening. I did drink steadily. To begin with, I missed particularly the 6.30pm drink.’

He enjoys going out in the evening just as much as he used to, with only one noticeable difference.

‘‘There always comes a point when people who are drinking suddenly seem to shout at each other. The volume goes up. I assume it’s because they’re drinking and losing their inhibition.’

Meanwhile, those super-sized clothes lurk in his wardrobe as a reminder to stick at his new regime.

‘It’s now incorporated into my life — it’s not really a diet,’ he says. ‘But, still, I feel that there is a great danger of me putting it back on again.

‘When I do have two meals a day — which I do sometimes; I don’t stick rigidly to one meal a day — I think it’s all slipping away again.’

That’s why, he says, he’s kept most of his old clothes: ‘I’ve always assumed I’d go back to them.’