Lay the crab on its back, twist off the claws and legs, and set aside.
Use the palm of your hand to push down on the crab. Then get your fingers between the gap where the body meets the shell and pull upwards.
Pulling quite hard, completely separate the crab body from the shell – it should come away in one piece.
Pull away and discard the feathery gills (also known as dead man’s fingers) – these are found around the main body and inside the shell.
Use a spoon to scoop out the brown meat from the shell and transfer it to a bowl.
Use a heavy knife to cut the main body in half.
Using a lobster pick or skewer, pick the white meat out of the cavities in the body and put in a separate bowl. It’s worth taking your time to do this, as there is a surprising amount of meat in all the small crevices.
Crack the claws and legs using a heavy object like a kitchen mallet or rolling pin – try to break them with one sharp tap. You don’t want the shell to shatter into very small pieces as they will be difficult to find.
Carefully remove the meat using a lobster pick or teaspoon. Discard the cartilage in the middle of the claws and legs. Put the meat in the bowl with the other white meat. Check the bowl for stray shell by shaking it from time to time – shell fragments ‘ping’ against the side of the bowl and can be removed.
Give the empty shell a good scrub and use a pair of kitchen scissors to neaten the edge of the cavity. Mix the brown crabmeat with enough fresh breadcrumbs to stiffen the meat. Season with salt and pepper, the cayenne pepper and lemon juice.
Spoon the white crabmeat back into the shell, then top with the brown meat mixture. Scatter with parsley, if you like, and serve with mayonnaise on the side, along with the extra lemon wedges and buttered brown bread or toast.