Here you go - had to do the photos for it coz I couldn't find it on the internet....
Overlap your main leader (orange) and your tippet section (yellow) by roughly the length you want for your dropper (have the tippet length to your right):
Now throw an overhand loop so that the tippet length (to the right) and your dropper leg sit on top of the other two strands
Shove two fingers up from beneath the loop so they are pointing up at the sky....
...then rotate them anticlockwise until they point at the ground
Keep rotating them until they point up at the sky again (i.e. do one full turn)
Now catch hold of the tippet length and the dropper leg with the same two fingers (use your thumb on the same hand to help):
Then pull both tag ends (the tippet length and the dropper leg) through the loop:
Before you snug it down tight it should look like this (if it doesn't you've f@cked it up - undo and try again)
Wet the knot and hold all four tag ends and pull tight. Snip off the leg which points back up towards the fly line (yellow) and keep the leg which points down towards your point fly (orange) to use for the dropper:
Simply pimply (you can buy me a pint when you see me and join the WTT whenever you like)