It’s the two policemen with sub-machine guns on the door that announces change as you arrive at the Liberal Democrat conference in Birmingham. Guns and barriers have not previously been part of the Lib Dem way. Gone too is that sense of the whole food faithful, up from the non-conformist corners of Great Britain for a prayer meeting. Gone too the open-toed sandals, though not yet – amongst older male delegates – the beards.

libdemsandals 6201 Lib Dem conference: inside the belly of the yellows

The strand of ruthlessness that was castigated by Labour and Conservatives alike in some Local Lib Dem seat fighting operations, has finally delivered a political gathering that rivals the once “big two”.

Make no mistake; this conference does something that the Liberal Democrats (and Liberals before them) have not achieved in a century. They have achieved a gathering that is focused, professional, branded, and coherent.

The hall is very yellow, but despite its yellowness, rather nicely done. Its slogan is nicely understated- “In government, on your side”. Tri-partite politics in Britain may finally have come of age – at least for a moment.

For many Liberal Democrats at last year’s conference, power seemed to have discombobulated, even corrupted the purity of what some regarded as their eccentric roots. But this year there is a swelling, a puffing, a confidence even, and yes, a surprising enjoyment of the power of being in power.

So that wending my way to my nondescript conference hotel bed last night, the cacophony of sound in the foyers of partying hotels through which I passed was as dense and as loud as I have known at either Tory or Labour gatherings.

Follow the Channel 4 News live blog for the latest at the Lib Dem conference

It would be no exaggeration to say that central Birmingham rocked last night. Maybe it does every Monday night – I have no way of knowing.

But anyone who expected a hangdog, hate Clegg, hate Cameron, dissatisfied coming together here would be disappointed.

For now, the Lib Dems have met coalition politics – for which town hall life has already well prepared them – and are enjoying it.

Despite their poll ratings and the last local election wipe out, there is an inescapable feeling of momentum here. It may be fragile – it doesn’t feel it. Yellow – which is everywhere – doesn’t yet feel like the historic building blocks of Red and Blue for the other parties, but it feels less cluttered by history than either.

The other party players on the UK national scene may have some serious adjustments to make to recognise the new scenery.

Follow Jon Snow on Twitter @jonsnowC4