Footage has been released showing the moment officers discovered the garage-turned bar over the weekend.
Officers found 12 punters and a barman drinking and listening to music behind the shutters of the workshop in Dudley Port.
Body-cam footage shared by West Midlands Police shows the moment the illegal gathering was brought to an abrupt end just after 7.30pm on Saturday night.
Tables and chairs had been set up next to the workshop, on an industrial unit off the A461, while a TV had been mounted on a nearby Land Rover.
WATCH the video here:
"Whether you believe it or not Covid-19 exists, doesn't it," the officer can be heard saying before telling the group they should know better.
The owner was hit with a £1,000 fine but the drinkers were allowed to leave without being punished after telling the officer "no argument".
Later that night, officers raided a nightclub packed with around 150 people near Birmingham's Jewellery Quarter.
After spotting taxis dropping people off on Buckingham Street, officers forced their way in and found people packed into two floors of the building.
The bar had been fitted out with neon signs and a dance room, and the building also contained a recording studio and gym.
Officers were pelted with bottles when they arrived in the early hours and drone footage showed some of the revellers fleeing via the roof.
Around 50 people are thought to have escaped punishment but 70 were given £200 fines and the DJ could now face a £10,000 fine.
One officer suffered minor injuries.
Assistant Chief Constable Chris Todd said: “Our officers continue to work long and hard to protect the public and reduce the spread of this deadly virus by breaking up these gatherings, often in really difficult circumstances.
“It’s unacceptable that our officers came under attack, and that one suffered a minor injury, just for doing their job and enforcing laws that are in place to keep us all safe.
“While there’s much to be hopeful of in terms of the rollout of coronavirus vaccines, people must remember that we are still in lockdown and the virus is still a real threat to communities across the West Midlands.
“We thank those people who are supporting our efforts to keep the public safe by sticking to the rules and staying home. They are saving lives.”
Home Secretary Priti Patel praised the officers for enforcing the lockdown rules, writing on Twitter: "Thank you to the brave West Midlands Police officers who broke up these gatherings - all while risking their own safety.
"Police officers will enforce the rules. They’re protecting the NHS."