For an artist of Billy Bragg's stature, it's not shifting albums or selling out gigs that concern him - though he's pretty good at both.
When you've been writing and performing music for 35 years, like he has, what really counts is remaining relevant, as he confessed to the sold-out crowd.
This was an intimate gig for a man more used to playing The Sage or Tyne Theatre these days - a far cry from venues such as the Mayfair and the Riverside, where he cut his teeth.
The good news is that he's got nothing to worry about, as his old protest songs carry as much resonance as when they were written, and his new ones address the disparate problems of the 21st century.
He's come a long way from the days when he was an angry young man with a battered acoustic guitar; for a start he's 60 next month, and while he might have mellowed, he's also learned lots of life's lessons.
His politics haven't changed much, and it's true that seeing him can be as akin to attending a lecture, as much as going to a gig.
But you won't find many hecklers at a Billy Bragg show, for the simple fact he's preaching to the converted.
His audience are largely lefties who agree that showing solidarity, working together and helping your fellow man when he is in need are the right things to do.
His songs have inspired many people over the years, not least tonight's support act, Sean McGowan, a young folk-punk-poet from Southampton.
He freely admits that Billy Bragg is his hero, and has been since he heard the song Tank Park Salute when he was 13.
It turned him to writing songs as a form of self-expression, and the fact his acoustic guitar carries a Joe Strummer sticker tells you a lot about his other influences.
He's just signed a deal with Xtra Mile Recordings to release his first proper EP after a couple of independent 'pay-what-you'want' releases, and he's improved a lot since I first saw him a couple of years ago.
Rather than being overtly political, his songs are about the grim realities of life, of being dumped by your girlfriend, or getting your head kicked in while standing up for a mate who then legs it.
He's got a wise head on young shoulders for a 24-year-old, and I hope he goes on to achieve the success of bedfellows like Frank Turner, because his songs certainly resonated with the early arrivals here.
On to the main man then, and the place was packed out to its 600 capacity by the time the one-time Bard of Barking took to the stage.
It was a different show to the last time I saw him, at The Sage four years ago, when he was touring his country folk/Americana album Tooth & Nail.
Then, he had a full band, tonight it was back to basics; mostly just one man and his guitar, though he was joined by CJ Hillman on pedal steel or electric guitar for a handful of numbers.
The setlist ran to two hours, including four encores, and started with an obvious crowd-pleaser in Sexuality (whose line "I've had relations, with girls from many nations" still makes me smile).
There were plenty of old favourites dusted off and given the rapturous welcome they deserve: The Milkman Of Human Kindness, Levi Stubbs' Tears and Greetings To The New Brunette were all given an airing.
There were dues paid to Bragg's own influences; Woody Guthrie's She Came Along To Me, a re-version of Bob Dylan's The Times They Are A-Changing Back, and his cover of Why We Build The Wall, by Anais Mitchell.
The latter features on Bridges Not Walls, the new collection of recent singles which this tour is promoting, and it struck a chord with its talk about "we build the wall to keep us free". Relevant indeed.
Climate change is the subject of King Tide And The Sunny Day Flood, the resurgence of the right inspired Saffiyah Smiles ("angry white men dressed like Elmer Fudd, shouting something about soil and blood", while Full English Brexit addresses the decision to leave the EU.
Waiting For The Great Leap Forwards was updated to reflect the modern-day targets of his slings and arrows, PM Theresa May, "orange gargoyle" Donald Trump and the far-right groups who disseminate hate.
The main set was closed by a huge singalong to the still-wonderful There Is Power In A Union, and the encores ended with an even more rousing A New England, complete with its extra verse as a tribute to Kirsty MacColl, who took it into the Top 10.
When you've more than a dozen studio albums under your belt there are bound to be some casualties; Between The Wars, To Have And To Have Not and Help Save The Youth Of America were all conspicuous by their absence - but, as Mr Bragg quipped, "at least he played The Man In The Iron Mask" .