The date of that 'party' was the 19th December and the Tier 4 lockdown came into effect two days later. A ragtag coalition consisting of Remoaners, the Daily Mirror, Alistair Campbell and Keir Starmer whipped up a storm over a pack of lies. I wouldn't expect you to know that, being in America, sadly many in Blighty are no better.
Might I also point out that Keir Starmer should have been run out of politics for his major cockups over Jimmy Savile, the various grooming scandals by Pakistani men and Operation Midland. He was the Director of Public Prosecutions who presided over each of those disasters.
https://medium.com/@lucynevitt/starmers-shambolic-cps-affabd38bb6d