Well, 70 years ago, Britain marked the end of WW11 with street parties up and down the country.

The Mall in London will be lined with picnic tables for 10,000 guests to enjoy a hamper-style lunch on Sunday 12 June next year. 7,500 tickets will be allocated guests from the Queen's charities and organizations, 1,000 will be made available for public ballot, and 1,500 will be provided to the event's official partners. Members of the public will also be able to share in the festivities at live sites situated in Green Park and St James's Park.
Source BBC.

He probably knew they were celebrating the end of the war called VE Day. Heck, he used to play on bomb sites close to where he lived. Apparently the street party marked the date when the World War II Allies formally accepted the unconditional surrender of the armed forces of Nazi Germany and the end of Adolf Hitler's Third Reich.
So street parties have a long history in London. But memories of those people who are still alive are hazy. At least photos show the reality.
Just how accurate are people's memories?

Blow me—knock me down with a feather—she told me I'd never been in Mr. Giddings' class. How could I have remembered him so well?
She had loved him. Lacking a father figure, she'd slipped a few times and called him Daddy. He firmly corrected the title. Perhaps she'd talked about him so much that I adopted him. I can even see him in my mind's eye—a short man with a kind face, standing beside the blackboard.
It makes me wonder how many of my memories are accurate. What's the use of writing a memoir if my information is incorrect? My internal chuckle might reach you through my words. I should write a disclaimer: All memories are my own and not to be confused with reality.
Maybe we could set up a group on Facebook. Let's call it, 'Correct Me If I'm Wrong.' We could share stories and others could chip in with their version of events.
You'd better check a particular memory of yours. It may not be precise.
Do you recall of events from long ago clearly, or are they hazy?