It looked so difficult, what with the very limited space, that I'd do it 'cos it's there'.
Or maybe its started burning coolant, and making clattering noises, so I should have a look; aaaaand, with the weight of the engine, combined with the lack of a hoist, I thought I might just be able to squeeeze my hands down there. Yep, that's it, that's the one.
Sorry, couldn't help it; and thanks for the answer.