Bring a medium pan (20cm or 8") of water to a boil.
Peel the shallot and dice it as finely as you can.
Remove the seeds from the chilli pepper and dice it as finely as you can.
By now, the water for the pasta should be boiling. Add salt (around 1 teaspoon) and cook the pasta until nicely al dente (10-12 minutes).
Approximately 7 or 8 minutes before the pasta is cooked, heat a medium to large (24-30cm or 10-12") frying pan or skillet over a medium heat. Add the butter, and when it has melted, add the shallots and cook without colouring for a minute.
Throw in the chilli then cook for another minute, stirring regularly.
Turn the heat up to high and pour in the wine and cook hard for 2-3 minutes, then reduce the heat to low.
Add the samphire and cook for 60 seconds.
Drain the pasta, reserving a little (75ml or ⅓ cup) of the cooking water. Add the pasta to the samphire, then mix and add as much pasta water as required to form a nice sauce.
Add the crab, mix to combine, then add as much lemon juice as you like to give the dish a nice "zing", then serve.