Soak the gelatine in a little bit of water in a small bowl until softened.

Meanwhile, line a 450g/1lb loaf pan or terrine with clear film (plastic wrap). Use some of the smoked salmon to line the pan, laying the slices widthways across the base and up the sides and leaving enough hanging over the edge to fold over the top of the filling.

Set aside enough of the remaining smoked salmon to make a middle layer the length of the pan. Chop the rest finely by hand or in a food processor. Take care not to over-process the salmon; it must not form a paste.

In a bowl, beat the cream cheese, crème fraîche, mustard and dill until well combined. Scrape in the chopped salmon and mix with a rubber spatula or a spoon until well combined.

Squeeze out the gelatine and put the sheets in a small, heavy pan. Add the lime juice. Place over a low heat until the gelatin has melted, cool slightly, then stir into the salmon mixture.

Spoon half the mixture into the lined pan. Lay the reserved smoked salmon slices on the mixture along the length of the pan, then spoon on the rest of the filling and smooth the top.

Tap the pan on the surface to expel any trapped air. Fold over the overhanging salmon slices to cover the top. Cover the whole pan with clear film and place in the refrigerator to chill for at least 4 hours, preferably 6-8 hours.