Billy Bragg has grown a beard. "It's OK," he assures, stroking it as all men with beards are wont to do, "it has spousal approval." It sits proudly on his face beneath a full head of silvery hair, and resembles a palette Dulux hasn't yet come up with: Autumnal Mischief, Marmalade Madras, Ginger Infusion. It suits him.
There is, he points out, reason for its being. Thirty years previously, when he was just starting out on a career in music, he dyed his hair blond. This had a profound significance for him.
"I looked in the mirror and saw a different person, not the same bloke who had just come out of the Army, but one with new possibilities." He tickles his whiskers and adds: "I think the beard might be a similar kind of thing. Transformational. See, I feel as excited about this new album as I did about [1983's] Life's A Riot."
For someone with a back catalogue as rich as his, this is quite a statement. Tooth & Nail, Bragg's first studio album in five years, is a reinvention of sorts. It's a record of bruised, sometimes embittered love songs in which he sounds both cast down and aside. As a body of work, it is redolent of a 55-year-old man staring down the barrel of his midlife crisis, tears welling in his eyes.
Over a smoked salmon sandwich in a central London hotel, Bragg argues that he has always written love-bruised songs; it's just that the political ones are the ones that have made his name.
"It's been a double-edged sword, that," he complains. "It allows people who don't really know me to dismiss me. I'm not running away from that label – political songwriter – and I don't mind it, not at all, but those people have clearly never heard my albums. I've always written as many love songs as I have polemical ones."
And it is the love songs, he insists, that represent him most fully, and to which he feels most attached. "They go deeper, far deeper than those songs prompted by something I've read in the paper."
Tooth & Nail's reflective mood allows Bragg to work his estuary vowels and glottal stops into a fine, melancholic croon. There are several songs here, but particularly "Chasing Rainbows" ("Please don't let my complacent mind belie my loving heart") and "Swallow My Pride" ("Can't live without you even though you make me blue") that lead the listener to only one conclusion: that his marriage is in tatters, and it's probably his fault. True? Carefully putting his sandwich back on to its plate, he says: "No no no no no. No. Look, I've been with my partner, Juliet, for 20 years now. We've had a great time, and we have a lovely son, Jack, who's 19, and who's been lucky enough to have had a lovely childhood. But, you know, we have our days when we crack our heads, when I don't live up to her expectations of me and when she doesn't live up to my expectations of her …. And this causes domestic friction. But the struggle in a relationship is where the sparks are, and I'm writing about things that frustrate me."
He smiles. "I'm not really a political songwriter at all, you know; I'm simply writing about things that frustrate me. Always have."
He adds that, lyrically here, he has taken certain artistic licence. In other words, two and two don't always make four.
"I've never left home like my character in 'Swallow My Pride' has, but have I gone a few days without speaking [to her]? I most certainly have. And have I been on tour and not phoned because I'm pissed off? Yes I have. If I were to suggest otherwise, my son would call me out as a liar."
The album is a significant one to him for other, more professional reasons too. It represents a return to the day job from which he feared he had, in some unspoken way, been demoted, cast out.
"I've been trying to find out where my niche is in the industry today," he says, as if unsure he has one any more. "Making an album as a self-funded artist is not cheap, and to promote it properly is expensive. I needed to be sure, in other words, that it was worth my while, because if I'm honest with you, no one is knocking on the door asking for Billy Bragg records any more."
He has, over the past couple of years, released the occasional song via his website, and these have invariably gone down well with the Bragg faithful. But would an album reach a wider audience?
"There is still a fanbase out there interested in what I'm doing, definitely, and they'll maybe come and see me play live, but that doesn't necessarily mean they are going to buy a new record of mine. When you aim high, as I have done on a project like this, it costs in blood and treasure. You want to know what the returns are likely to be before even trying to climb the mountain, because otherwise what's the point? But I'm proud of this record, and I'm hopeful it will go out there and find people, make its mark."
Billy Bragg started making music in the early 1980s. With a fairly tuneless voice, but an awful lot of heart, he effectively reinvented the protest song, and brought his dented impassioned anthems – about the miners, about Thatcherism, and, yes, about love too – to the masses.
By 1991, he scored a proper crossover pop hit in the wonderful Don't Try This At Home album, and then spent the next 20 years behaving much as one would expect of our leading troubadour: regularly appearing on Question Time, writing op-ed pieces for the broadsheets, and even penning a book about nationality and identity (2007's The Progressive Patriot).
In more recent times, Bragg tentatively toyed with the idea of returning fully to music while casting wary glances at his bank balance, and then busied himself instead with more philanthropic endeavours, among them his Jail Guitar Doors initiative, in which he took instruments into prisons, teaching his captive audience the benefit of expressing oneself through music. The years went by, and it was only after his mother died suddenly, in early 2011, that he decided at last to relocate that lost focus.
"I felt I needed to stop fannying around," he says succinctly. "Losing a parent can't not affect you, and make you think. It did me. It made me look into the very heart of what I was doing, and why. I wasn't wondering about how long I had left, nothing like that, but simply whether I was spending my time in a worth-while way. I think I'd been avoiding the issue for a long time." His voice is rising as he speaks now in that typical, earnest manner of his, lips pursed, fists clenched – and not altogether unlike, you find yourself thinking, a Member of Parliament when trying to get his point across to Jeremy Paxman. "I'm ready to challenge people's idea of who Billy Bragg is, and what Billy Bragg does," he says.
Sandwich finished, we make to leave. Before I go, I ask him about his son. Does he, Jack, have any musical ambitions himself?
Bragg smiles, his cheeks flush. "He's got himself a little band together, a three-piece," he beams. I ask him what they are called. "Oh, I can't tell you that. He doesn't want to be seen as The Son Of ... and I respect him for that. I love it that he's doing it his way. And his music is great, just great. He plays me his songs at home all the time.
"On my guitar mostly, because my guitar is downstairs, and it saves him the bother of going upstairs to fetch his. He plays it really well. I just wish he'd put it back afterwards, when he's finished. But he doesn't, never, not once."
'Tooth & Nail' by Billy Bragg is released on Cooking Vinyl tomorrow
1957 Born Stephen William Bragg in Barking, Essex.
1982 Fresh out of the Army, and under the name Spy Versus Spy, he comes second in the Bridge House Talent Contest in Canning Town. "I got a little bit of wonga for it, and I've never looked back."
1983 Releases his debut album Life's a Riot with Spy Vs Spy.
1985 Bragg's song "A New England" is covered by Kirsty MacColl, and becomes a Top 10 hit.
1991 Releases his most successful album to date in Don't Try This At Home, which includes the single "Sexuality".
1994 Becomes a father, with partner Juliet, to Jack.
1998 Teams up with American act Wilco on the album Mermaid Avenue, setting some unrecorded Woody Guthrie lyrics to music.
2007 Publishes his book The Progressive Patriot.
2013 Releases his first studio album in five years, Tooth & Nail.