Slice the pork fillet lengthways once or twice depending on thickness, then cut into ¼" (5mm) slices.
Mix up the marinade and cover the pork slices. Set aside to marinate for 30 minutes.

Cut the vegetables into half lengthways (unless they are quite thin) and slice into nice diagonals, about the thickness of pound coins. Keep the asparagus tips and brocolli florets whole. Put each pile of sliced vegetables aside in separate bowls.

Drain the meat of marinade.
Heat the wok, add a splash of oil and fry the pork until browned and set aside. Do this in two batches if necessary to keep the wok hot. If you get a lot of water building up, scoop out the meat, pour the water off into the marinade, and start frying the meat again.
Mix together the left-over marinade and the sauce ingredients.

Keeping the wok hot, and adding oil as necessary, fry each of the vegetables, starting with those which will take the longest to cook. Set the vegetables aside in another large dish as the wok fills up and carry on frying.

When all the vegetables are done, clean out the pan, then re-fry the pork, then add the noodles and another generous splash of oil. Fry the noodles until warmed thoroughly, then add the sauce mixture. Stir the sauce through until it thickens around the noodles.

Either throw the vegetables back in and stir everything until well mixed and piping hot. Or tip the noodle mixture out into a serving dish, reheat the vegetables and pile them on top.
Serve.