For a vegetarian version, simply top with half a cherry tomato or slice of radish.
Place the cream cheese in a bowl with the horseradish, dill, lemon juice, zest and a pinch of salt and black pepper. Mix together and chill in the fridge for up to 1 hour, if you have time, to allow the flavours to develop. You can always add more horseradish later, if needed.
Cut the cucumber into 1cm-thick slices and carefully scoop out some of the seeds, making sure not to go through to the bottom.
Arrange the cucumber slices on a platter and distribute the cream cheese mixture evenly between them, neatly filling the centres.
Cut the smoked salmon into strips. Roll up and place one on top of each piece of filled cucumber. Garnish with dill sprigs or chopped chives and a sprinkling of black pepper.