100's of 1000's of report server jobs added - how to kill all?
I was wrong in my assumption that Notifications was not the table to be looking in. It was exactly the right one. Deleting all where the ReportID matched the one we were looking at fixed the problem.

DELETE FROM [ReportServer].[dbo].[Notifications] WHERE ReportID = '4837A901-7188-4FCB-B86A-7974D35D9F56'