I can testify to a blowing Miltek at that exact point causing it to fail its MOT :O(.
Theres no gasket just that stupid clamp! I put a good seal of high temp silocone sealent on it and around the clamp and it did the job! Seems to be holding well so far.
Shame that I can't say the same about the welds on my back boxes!!! They are blowing but at least Miltek are sending me out a new rear section.
Theres no gasket at that joint, and it's the worst one to try and get to seal properly IMO.
I'd get a new clamp for it, undo the joint and clean off any paste/gum/crap, clamp it up with new clamp and seal with a silicone based sealant