An additional 95,000+ records are now accessible in the FMP version of the 1939 Register for England and Wales. These are usually batches of records unredacted as people pass their 100th birthday or their death is reported.
Interestingly, if you search the database for people born in 1921 there are 8,464,807 results. That’s almost ten times the number with births registered that year! It’s equally large for prior years. The total appears to include about 8 million records with no name or date of birth.
Find out more about the 1939 Register at https://www.findmypast.co.uk/1939register