TD5 Gear box screech

Hi folks. I wonder if anyone can give me any clues as to what's behind an alarming noise my 2002 TD5 (85000m) defender has developed?

Suddenly in the last week there is a terrible high pitched screech which sounds like it comes from the passenger footwell area or gear box when increasing through the revs. It happens in any gear but only for a second or two while brisk accelerating (nothing when "normal" Landy driving). Gear changes are smooth (surprisingly!) and no other clatter or noise from gear box or clutch.

I am at a loss as to what's causing it. Any ideas?

Post in the TD5 or Defender section and/or do a search under "exhaust manifold gasket leak"

Could be the inlet manifold gasket. I had this replaced on mine and it sorted the screech. I don't suppose the head come off at some point before this started to screech?