On Mon, 28 May 2018 17:22:51 +0100, Graeme wrote:

Kept poking at the end of the two storey downpipe until a tiny amount of
water began to trickle, so kept going and suddenly a thick mass of mud
and leaves shot out, followed by two storey's worth of the most foul
smelling water I have ever encountered, which of course splashed over
everything including me.

Is there a video? Knowing how fast a down spout empties itself when
the blockage lets go I think you are are understating things. I've
only encountered 4' of down spout and about 5 m of full deepline
gutter. One gets very wet, very quickly, even if you know it's going
to happen and you run away the moment it starts. B-)

--
Cheers
Dave.