Clean the mussels thoroghly and discard any which do not close tightly when lightly tapped.
Put the vegetables into a heavy lidded flameproof casserole with the scrumpy and pepper. Bring to the boil then cover and simmer for a few minutes until the vegetables are tender.
Open the casserole and add the mussels, stirring once or twice. Put the lid back on and steam for 5 minutes until opened.
Serve from the casserole with bread to mop up the juices. A dollop of clotted cream can be added to enrich the sauce.