Hemp was introduced to British coarse fishing by Belgian refugees during World War I. They used it to catch large numbers of good-sized roach from the Thames. By the 1930s hemp was so popular and successful throughout the country that many angling clubs banned it from use on their waters. Some people said it drugged roach into a feeding frenzy, others thought it took root and grew underwater. Fortunately, common sense prevailed and there is now fewer places that still have it banned.
 

Hemp can be bought ready cooked from most tackle shops, but it is much cheaper to buy it raw and prepare it yourself.
Put four parts of water to one part of raw hemp in a saucepan. Bring to the boil. Add half a teaspoon of Bicarbonate Soda. Turn the heat down to a simmer. After about half an hour the seeds will start to split open and white shoots will appear from most of them.
Take the saucepan off the heat and strain off the water into a container. Hold the strainer under a running cold tap for a minute to cool the hemp and prevent further cooking. If you cook the hemp for too long, it will open too far and be too soft, it won't stay on the hook.
Stored in a fridge, hemp will keep fresh in an airtight container for about a week. Hemp also freezes well, allowing batches to be prepared in advance and any left after a session can be re-frozen. Freeze it in air-tight polythene bags.
TIP - The water that was strained off the cooked hemp can be used to mix up groundbait, enhancing the flavour and attracting qualities.