Just noticed a small wet patch under my Defender. The structure (pump??) under my alternator appears to be leaking a blue liquid. My screen wash is blue and also my radiator fluid (antifreeze), so don't know what it is or where it is coming from. Please excuse my ignorance but if someone can help me explain what this blue liquid is and what is the likely problem I would be most grateful. Is it likely to be a new pump, new seal or new pipe? Guidance on what further action and what to do next would be appreciated. Picture enclosed. Thanks.

What i would do is taste it. I know, it sounds disgusting but if it's sweet, it's antifreeze. If it's soapy, it's washer fluid. Don't go drinking the stuff, just a dab on your finger

Looks like it's antifreeze though, let's be honest, why would washer fluid be going to the pulley/alternator area?

If thats a 300tdi? google P seal leaking, if it is the P seal get it fixed as the coolant level drops, system overheats as water pump is high mounted then either head gasket goes or the header tank or both!

As above. P gasket, sounds likely, but it could be any of the hose connections onto the engine. See if you can feel round each hose end for wet. P gasket water normally runs down the front of the block behind the alloy housing.