Hi Liz
Although I can't confirm the year of the disintegration of the fly wheel, I was working in the Times Office at the time and remember going to work in the morning after, and shown the quite large portion of the fly wheel which had crashed through the roof and ended in the machine room, two floors below.
Thankfully nobody was on overtime !!! so there were no injuries.
Now the year escapes me, but it would have been between 1950 and 1955,
sorry I can't help you any further.
Roy