Neither of my parents could have worked until the (current) state retirement age due to different health issues. Luckily, they were able to retire in their early 60s. And now a family friend has just retired aged 64. His state retirement age is 67, but due to worsening arthritis and the feeling that he's slowing down physically and mentally, he's sure that he couldn't manage another three years.
I accept that this country is experiencing a democratic time bomb due to the ageing population, but just because the Treasury needs people to work longer, it doesn't mean that they'll be able to. I know there are people in their 70s and older who are still fit for work and that some of them enjoy working, but I think they're in the minority.