Peel the cucumber, cut in half and cut into slices about 2 cm thick.
Mix all other ingredients in a pan and bring to the boil while stirring. Add the cucumber and cook gently for 10 minutes over low to medium heat.
The sauce becomes relatively thin, I like it that way, otherwise you could add half a teaspoon of Maizena to the cold sauce and then bring it to the boil, so that the sauce becomes a little thicker!