Can't delete bogus subscription

I created a subscription from a backup file / publisher, but something went wrong along the way. 

Now I've got a subscription that I want to remove (to clean up), but when I try to remove the subscription either via SSMS or try to generate a script, I get the following error: 



any ideas with this? IT's not urgent, but would like to remove the bogus subscriptions from SSMS.

Thanks,

Chris