leaking small cover plate

Wondered why one of the KV6 Rover 75 s I have was loosing small amounts of water over a week ,thought here we go again,water pump etc.

Checked under the car and found the weeping is coming from a small cover plate high up on the engine sort of above the oil filter but the the rear of the engine,maybe attached to the rear head .Has two small bolts and appears to be a small oval shaped cover plate.

Anyone know what this is for,what its called and is it an easy fix.

Pig of a spot to get to though.

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