We have seen this before. It is easy to forget, amid all the tries and sunshine, that rugby has a darker side too: a wet, windy, deafening ferocity that not even the most twinkle-toed can transcend. And they practically invented it here.

This is not the first time Leicester have welcomed their beloved neighbours to the lair as champions and disabused them of any notions of grandeur. It took the Tigers 40 minutes to whip themselves into the necessary fervour, but when they did, all else followed: the rocking stadium at capacity, the win, the bonus point, the obliterated opposition.

"The crowd was brilliant," said Geoff Parling, Leicester's head coach. "The crowd is outstanding. This stadium is iconic. It's rustic, I know it is. I've said it before. It's old. But I wouldn't change it for the world."

It was not just the 40 minutes of directionless fumbling by the home team, but a mass fracas with a number of those visiting friends, which spilled into the stand, that sparked them into life, pretty much from the moment they re-emerged from the break.

The second-half Tigers showed the first-half version how a lineout and drive is executed, when Jamie Blamire scored their first try within four minutes of the restart. That earned them a one-point lead and normal service was resumed.

Half-time's highlights analysis probably centred on that, well, we can't really call them fights these days – this is the age of the camera, after all – but certainly pushing and shoving long after the referee had brought the first half to a close.

There were Alex Coles and Freddie Steward at each other's throats. On it went, up the steps of the Crumbie Stand, where Henry Pollock, obviously, seemed more interested in tying his shoelace than getting in for an orange. Ollie Chessum and Steward, his England teammates, did not find it funny, shoving him all the way to the changing room.

"These games are going to be hostile," said Phil Dowson, the Northampton coach. "In the current game, you can't throw anything. It's just push and shove and talk crap. That happens every derby. So I don't think that had any impact. It's not as if anyone got filled in. Well, you just can't any more."

Such discord was in keeping with a first half in which neither side could quite find their feet on the slippery turf. Saints seemed more in tune with the kind of rugby that has prevailed before the rains came. Theirs was the only try of the first half, early on, when Finn Smith, with an advantage, chipped in behind, where Billy Searle spilled, and James Pater gathered to score.

Leicester could not make anything of a stream of penalties in the first half, sending four of them to the corner in the first quarter and spilling or, often, not even securing the subsequent possession. How that was going to change.

Once Blamire's try had restored order, the Tigers tore through the Saints at set piece and high ball. The champions deteriorated in the swirling rain.

Cameron Henderson was next to rise to take a lineout, after a ferocious scrum had earned the penalty. Henderson then finished in the corner like a winger, sent away by Gabriel Hamer-Webb. That put Leicester six ahead and five minutes later they were more than a score clear, this time Finn Carnduff finishing after another attacking lineout.

The bonus point came in the final 10 minutes after one of the more bizarre swings of fortune. Smith's cross-kick had sent George Hendy away from his own 22, Adam Radwan's slap-down earned him a yellow card. But way back earlier in the move Tom Lockett's head had collided with Solomone Kata's. It was another totally innocent accident, Kata not only changing direction, but rising sharply to clash with the covering Lockett.

Even by rugby's standards, the yellow card was absurd punishment. But it also meant Radwan's was rescinded. On he came, off Lockett went, and over strolled Steward for the bonus point from the subsequent lineout.

When it is not your day, it is not your day, Saints must have rued. But when it is your day, especially at this grand stadium on a wet and windy afternoon, it really is.