Thank you but I have now found a simpler solution.
1. Execute a safe boot with command line access;
2. Login to built in Administrator account;
3. At command prompt execute command "net localgroup administrators MyAdminAccount /add";
4. Then restart and elevated rights have been restored to...
Hopefully someone can help or confirm that a reinstall is the only solution
In addition to my user accounts, I created a specialist admin account with elevated rights
I don't know how I did it but I accidentally removed the elevated rights from my administrative account so now it is a user...