Mix the shrimp with the Worcestershire Sauce and sesame oil, toss them with the cornstarch, and leave to marinate for 15 minutes.
Heat a generous amount of oil in a suitable pan and quickly brown the shrimp on both sides until the cornstarch coating is just getting a little crispy and then remove them to a bowl.
Heat a tablespoon or so of the oil in a saute pan over high and add the sugar, vinegar, ketchup and ginger. Cook, stirring briskly until the contents of the pan thicken to a glaze.
Lastly, stir the shrimp into the glaze and, when they are heated through, toss with the sesame seeds and serve immediately.