Set up a jelly bag. If you havent got one it is very easy to improvise. You will need 1.25 metres of butter muslin, folded in two. Upturn a kitchen stool on a table and tie the four corners of the muslin, one to each leg of the stool. Stand a wide mixing bowl on the seat to catch the liquid. Wash and dry the crab apples. Cut in half. Leave the skins and pips as they help to colour and set the jelly. Place in a preserving pan or large saucepan. Cover fruits with water. Bring to the boil, then simmer for about 30 minutes, until apples have fallen to a soft pulp. Pour pulp into jelly bag and leave to strain overnight. Do not push pulp through or squeeze the bag, it will result in a cloudy jelly. It is not something you can hurry. Wash five 1lb jam jars in hot soapy water, rinse thoroughly and place in a low oven to dry. Measure liquid. Allow 1lb sugar to every pint. Dissolve sugar in a liquid in a preserving pan or large saucepan. Bring slowly to the boil and keep it at a rolling boil for about 20 minutes. After 15 minutes add several sprigs of thyme and start testing for a set. Use a long handled wooden spoon to stir the jelly. Turn the spoon with the back facing you. Wait until the liquid flakes down the back of the spoon and drips off, leaving a long, blobby drip like an icicle which adheres to the spoon. This will give you a set. Remove the thyme stems. Pour jelly into warm jars and cover with a waxed disc. Allow to cool for about 30 minutes. Remove the wax discs and drop in thyme leaves and flowers. Stir gently with the tip of a clean knife to disperse thyme through the jelly. Top again with waxed discs. Cover pots with lids or cellophane. Label and store in a cool, dry place.