Preheat oven to 180 C / Gas 4. Grease a 450g (1 lb) loaf tin.
Turn salmon tin contents into a bowl and remove and discard any skin or bones. Flake with a fork and stir in the breadcrumbs.
Melt margarine in a saucepan. Add flour and cook for 2 minutes. Stir in soup and cook, stirring continuously, for 3 minutes. Add to salmon and mix well. Remove from the heat. Add the beaten eggs and season. Pour into the prepared tin.
Place tin in an ovenproof dish and pour in water up to 1cm (1/2 in) high.
Bake in the oven for 60 to 75 minutes. Remove from the oven and leave in the tin to cool.
Run a knife around tin edge and turn onto board. Cut in slices and garnish with sliced cucumber.