Derbyshire 170 for 5 (Wood 63*, du Plooy 57) beat Birmingham 167 for 9 (Pollock 46, Scrimshaw 3-23) by five wickets with five balls remaining

A large-scale pitch invasion marred the end of the T20 Blast game between Birmingham Bears and Derbyshire at Edgbaston.

Several hundred spectators - mainly students attending as part of a promotion - ran on to the pitch at the end of the match. While there was no sign of any malicious behaviour, the scale of the incursion may cause repercussions for a sport currently making a case for greater crowd numbers at games.

Ironically the student event was named 'Invades'. The promotion promised 'free flowing pints' and 'exclusive drinks deals'.

No players were hurt - or even approached - though several stewards and some of the groundstaff did become involved in altercations as they tried to prevent spectators, many of whom were wearing fancy-dress, running on to the outfield. In the time of Covid, such behaviour is likely to make authorities uneasy. It may be worth noting that Selly Oak, just a mile or two down the road and where the University of Birmingham is situated, has seen a rise in Covid cases of almost 800 percent (actually 791.7) over the last week.

Edgbaston is one of the grounds that has just been included as part of a pilot event for the limited-overs series against Pakistan and Sri Lanka. At least 50 percent capacity had been expected at those games, though those numbers are due to confirmed in the coming days. There appears to be a genuine concern at Warwickshire, at least, that this incident could have compromised those plans.

"The behaviour of a small number of students after the match finished was disgraceful," Stuart Cain, Warwickshire's chief executive, told ESPNcricinfo in a statement.

"The organiser behind their attendance was well aware of social distancing requirements and these were communicated to everybody who bought a ticket. They were then enforced as best as possible on the evening by stewards who worked incredibly hard to manage their behaviour. Messages were repeatedly broadcast over the PA system and screens, and pitch invaders ejected. They will receive a life ban if identified.

"With society having spent the last 15 months managing the pandemic, to see a small number of people behaving in this way is heart-breaking. We apologise to the majority of spectators who respected social distancing measures. I will not let this company or crowd come to Edgbaston again."

There had been a succession of streakers throughout the game. While the venue had already shut its bars to the students and attempted to disperse groups who were not observing social distancing, it soon became apparent they were hopelessly outnumbered. In the dying moments of the game, the trickle of students became a stream until, after the last ball was bowled, the dam burst entirely. With venues required to demonstrate they can handle the return of crowds with the requisite Covid protocols, pictures of hundreds of spectators on the pitch may not inspire confidence.

Some will say the stewarding was insufficient. But with crowd numbers limited to 25 percent of capacity at present, clubs are struggling to make these games financially viable for spectators. There were around 6,000 in the ground in total, about 2,000 of which belonged to the student party. After the game, reports emerged of at least one spectator having been hurt by a thrown object.

"The atmosphere was horrible," one spectator told ESPNcricinfo. "I have never, in 50 years at the club, been at anything like it. I the club wishes to continue to advertise Edgbaston as a "fortress" and encourage excessive drinking and partying at the expense of appreciation of cricket, I'm out of there.

"It was a disaster waiting to happen and a gross error of judgement on the part of the senior management team. Heads should roll."

It probably could have been worse. Not for a moment did any of these pitch invaders look as if they had any malicious motives, and all of them were dispersed within about five minutes. But it will raise questions about both the stewarding of such events and the wisdom of marketing them in connection with alcohol promotions.

The other shame of the incident was that it detracted from an impressive victory from Derbyshire and a match-winning innings from Tom Wood, in particular.

Wood is a cricketer who has taken the scenic route into the professional game. He is aged 27 and having his second stab as life as a county player after being released by the club at the end of 2017. This was just his fifth game in the format.

But he ensured his side held their nerve just as it appeared they may let Birmingham Bears back into a game which Derbyshire had dominated throughout. Having added 90 with Leus du Plooy - Derbyshire's highest partnership in this format against Birmingham - he saw his side add just 25 runs in a five-over spell in which they also lost three wickets.

It was also a significant result for Matt Critchley, in his first game as Derbyshire captain. Coming into this game, Derbyshire had won just one of their six most recent T20 games and lost the last three. Partially as a result, they decided to rest their regular captain, Billy Godleman, for the rest of the T20 campaign to allow him to "recharge his batteries".

While Critchley has never previously captained at professional level, he was the natural choice as a player of increasing stature in the Derbyshire dressing room and here he marshalled his resources nicely as his side pulled off a win against the side that was top of the table little more than a week ago.

To put the achievement into perspective, it was only the second time Derbyshire have ever defeated Birmingham (or Warwickshire, as they were once known) at Edgbaston in the 18-year history of the format. The previous occasion was in 2011.

While Birmingham's total may look respectable, on this surface - a hybrid track offering the sort of pace and bounce that's ideal for these games - they were well short of par. While there were moments when Ed Pollock, whose ability to slog-sweep sixes off seamers is remarkable, looked as if he could carry them to somewhere around 200, they never really recovered from losing three wickets in the first 19 balls of the match.

Most pertinently, they never recovered from the rare failure of Sam Hain. Hain came into this match averaging over 70 in the campaign this season but here, coming down the pitch to his second delivery, he was cramped for room as Fynn Hudson-Prentice angled the ball into his body. Hain looked aghast at the decision, but the umpire felt the ball had brushed the glove on its way to the keeper.

Perhaps the surface helped Derbyshire. Whatever their results, their attack does not lack for pace and here they seemed to enjoy the bounce and carry in the surface. Conor McKerr, on loan from Surrey, claimed two wickets in his first over, while George Scrimshaw's figures were the best of his short career in this format.

The Bears were not at full strength. Dan Mousley was absent having broken his finger in training, while Rob Yates is unwell and Jake Lintott is in isolation having tested positive for Covid-19. They also left out their overseas player, Pieter Malan, who scored 63 against Northants only a couple of innings ago.

It's a result that does nothing for Birmingham's hopes of qualifying for the knock-out stages. After four victories in succession, they have now failed their last three - albeit one of them fell victim to the weather - though you suspect it is the crowd invasion that will most concern the Warwickshire management in the coming days.

George Dobell is a senior correspondent at ESPNcricinfo