Green Oil Degreaser

Clean Chain degreaser makes chain cleaning easy.
Put it on your chain. Spin the cranks for a few seconds.
Rub it off with a dry rag, then repeat with a wet rag or brush. Then rinse.

One bottle does 7 - 10 chains.
One bottle can also make a whole litre of Green Clean bike cleaner - just mix with 900ml of water.