Deja Dup and Ubuntu One backup problem

[Colin Law]

I am using Deja Dup to backup onto Ubuntu One server from Ubuntu
12.04.  This has all been going well until now.  I see from logging
into ubuntu one that I have used up all my allocated space and when I
run the backup I get a backup failed with status code 502, and if I
run deja dup with debug enabled I see that there is an error
Backend Exception: Upload will exceed quota.

I thought that it was supposed to remove old backups if necessary to
make space but it does not seem to be doing this.

Google has not provided any help.  Any suggestions anyone?

Colin