To satisfy my curiosity I removed the existing C28 to see if that would make a difference but to no avail - my DMM (not Fluke) still reading 1
I unsoldered one of the speaker tags and measured 0.8 ohms across the secondary??
Looks like the primary is open circuit and will need replaced - rewinding may be a bit beyond me at this stage. Although the new transformer from RS looks attractive that would be too easy!