People (like me) born before 1956 often left school at 15. Today, children have to stay in FT education or do an apprenticeship until they're 18. Very few people of the older generation (around 10%) went to uni, and gap years weren't a thing, so full-time working life started, on average, much earlier.
Women born in 1955, leaving school at 15 will have to work for 51 years before getting their SRP. Someone leaving school today will start work at 18 and their (current) retirement age is 68, so they will only work for 50 years. If, as is commonplace, they take a gap year and then go to uni, they won't start their career until they are 22 and at present will be able to get the SRP after only 46 years.
So raising the retirement age has had the biggest impact on women, and on the oldest women.
I think the changes have been far too quick. They should have been more gradual, and there should have been more effort put in to make sure that the dates for every woman were communicated to them individually much sooner.
I knew at 40 that the ages were going to be equalised, but I didn't know that full equalisation would be in place when I was 63. That came later, after poor health had forced me to switch to a much less lucrative job. Had I known that my working life was going to be a full 6 years longer, I'd have struggled on, had loads of sick leave, and probably got an ill-health retirement with extra years added to my public sector pension.
The extra year added in 2010 or whenever it was like a slap in the face.