Slice cucumber diagonally as thinly as possible and place in a large, shallow bowl. (Try using a vegetable peeler, cheese slicer or mandoline to get thin slices.) Warm the vinegar in a small saucepan and add the sugar and salt, mixing until dissolved. Add the mint and Tabasco and remove from heat. Immediately pour over the cucumber and mix well. Allow to cool to room temperature, then cover and refrigerate for 1 hour or overnight.
Just before serving, cut the baguette and drizzle with olive oil. Slice the lamb thinly and arrange on one side of the baguette. Top with the cucumber, season with salt and pepper to taste and top with other half of baguette. Repeat for other baguette.
TIP: The mint-pickled cucumber can be made a day ahead and refrigerated in a sealed, non-reactive container (e.g. glass). The roast lamb will keep 2-3 days, covered, in the refrigerator.
