Hackney MPS tweeted about the incident on Sunday, when balmy temperatures lured thousands of people out of their homes.
Patrolling officers found the small group sitting at a small picnic bench in Victoria Park, which had been shut as part of a social distancing crackdown.
Following the encounter, the force wrote: “The park is currently closed to the public yet we’ve discovered three males had jumped the fence to have a sit down picnic on a bench drinking beers!
Under current Government measures, Brits can only leave the house if they are key workers travelling to their jobs, shopping for health essentials, or to take exercise once a day.
New emergency powers granted to police mean they are able to serve on-the-spot fines of £30 to anyone ignoring stay at home orders.
Hackney’s officers proved in an earlier tweet that they were sticking by official instructions to the letter.
For avoidance of doubt - kite boarding, drone flying and picnicking are not essential activities... SCs from @MPSTowerHam @MPSHackney conducting proactive patrols and assisting response teams across the BCU #StayHomeSaveLives pic.twitter.com/vuaJj66bwx— MPS Specials (@MPSSpecials)April 5, 2020
Writing from Well Street Common, they said: “Reading a book in the park is not an essential reason to be out.”
“Stay home save lives, protect the NHS and other key workers.”
Meanwhile volunteer officers from the Met's Special Constabulary added: "For avoidance of doubt - kite boarding, drone flying and picnicking are not essential activities..."
And in south London, Richmond Police issued a video plea to the public.
This message is being echoed across areas of #Richmond
Keep yourself, family + @NHSuk safe#Stayhome unless essential
We moved people on for sun bathing, meeting friends etc.
Think of the people in hospital or the families of those who have lost their lives - #StayHomeSavelives pic.twitter.com/gtwGBBi214— Richmond Police | #StayHomeSaveLives (@MPSRichmond)April 5, 2020
It tweeted an announcement made by one of its officers urging people to "go home" because there were too many people in the area to "implement social distancing."
Alongside the clip, the force wrote: "This message is being echoed across areas of #Richmond
"Keep yourself, family + NHS safe. Stay home unless essential
"We moved people on for sun bathing, meeting friends etc.
"Think of the people in hospital or the families of those who have lost their lives - #StayHomeSavelives."