If this is a "standard style" ladder, then at the top of each vertical you
will find blanking plug (on one side) and bleed point (on other side).
Isolate ladder rad by turning off both lockshield and handwheel/trv valves.
Remove blanking plug at top.
Feed decent bore size (6mm min) nylon tube into one leg of rad from top.
Make sure that your tube is long enough to reach the bottom of the rad leg.
Syphon out contents into nearby bog! (don't swallow any though).
Follow others' advice about catching any remaining water when undoing
valves/removing rad.

Phil

Phil - This is interesting... how does one syphon out the contents ?
Do you mean suck on the end (without swallowing!) and drain it all
out ?

If so... does this get *everything* out bar a few drips or am I going
to still have a substantial amount remaining inside ? It doesn't
matter either way, but would be good to be prepared...

Andrew