Sleaford Mods @ O2 ABC, Glasgow, 19 Oct

Sleaford Mods may be the most unlikely stadium act of this or any era. The Nottingham-based duo are not yet at the stage of booking Hampden or Wembley for their next tour, but given their surging popularity, it's no longer beyond the realms of possibility. Few artists make their Glasgow live debut at a venue as small as Broadcast, and go on to pack out a hall the size of the O2 ABC within two years. But that's exactly what Jason Williamson and Andrew Fearn have managed tonight.

When The Skinny first spoke to Williamson in 2014, he was days away from quitting his job as a benefits adviser. Those taking the plunge into full-time music often wonder how long it will last – will I be signing on within a year? – but there's little chance he'll be back working 9-5 anytime soon. Consider the evidence: the Mods' profile continues to grow; they've signed a record deal with Rough Trade, and have their terrific new TCR EP out now (14 Oct).

It's worth reminding ourselves how unlikely all of this is. Fearn composes bleakly minimalist soundscapes, which act as a foundation for Williamson to spit out lyrics on subjects ranging from German hostel toilets to sleazy work colleagues. This is not office party karaoke material. "It takes a lot of effort to write these songs," Williamson deadpans. "It's not just shouting and swearing." But that's still a prevalent attitude among non-believers – Noel Gallagher dismissed them as "two guys... shouting about fucking cider and fucking shit chicken."

But the Mods have never been about misery. While it's easy to relate to stories of joyless employment or crippling hangovers, what makes Williamson's lyrics so enjoyable are the put-downs. In new track TCR, he tells a surly young barman to "go and listen to some fucking garage punk, you pointy little tit." In Fizzy – perhaps the signature Sleaford Mods tune – the crowd roars along with glee as the frontman describes a former office manager as wearing a "shit-fitted shirt" and white Converse.