Since England's last and greatest Queen Mother* lived to the age of 101, we might listen carefully to anything she said. Amongst her pearls (verbal ones, that is) was the suggestion to dance. In one of those many interviews when reporters asked her how she had stayed so spry, she answered that you have to take exercising a little at a time and do what you think is fun.
An English campaign that may have taken off from these comments is trying to persuade over-50s to spend half an hour a day exercising. While earlier admonitions had told people to exercise vigorously three times a week, current "experts" believe that a gentler regime will be better. It certainly might have more appeal and be more lasting.
A vigorous exercise program should be approved by your doctor, but gentle stretches can be done by almost everyone. Combatting stiffness applies to people of all ages and walks of life.
Small stretching at home or the office can be quite practical. If you make yourself get into a routine of frequent stretching, you will really feel a difference in your mobility.
Try keeping a tennis ball close to your telephone and/or the TV. While you're talking or watching, squeeze the tennis ball as hard as you can three times; then put it down. Keep repeating. This is good for the wrists, the most common point of fracture in older people.
While you're sitting at the computer or almost anywhere, you can take little breaks to stretch your neck, gently turning from side to side alternately with looking down.
Tightening the stomach muscles is something you can do, and no one else will even notice.
If you don't have a palace or a dance floor handy, you can check out a dance video from the library and swing along anytime you like. Dedicate a few of your moves to the Queen Mam.