Forced Icloud password change

Hi, Since about 30 minutes ago, when I log onto Icloud from my Google Chrome browser on a Dell Windows PC, I'm being asked to change my password - enter current and then enter and verify a new one. The only option is to do this, or Cancel, which just goes back to the login screen i.e. I am unable to log into Icloud without changing my password.

My current password has all of the characteristics of a secure password - 11 digits long, contains upper and lower case alpha characters, and numbers as well. I'm a little suspicious, so thought to check on here if anyone else has had this. Interestingly, when I logged into this Community page, I was not presented with the same request - I just logged straight in.

I've now gone back to the Icloud login page, after logging on here, and it is still forcing me to change my password.

Cheers

Neil