Mix the seitan ingredients together in a large bowl, and knead well until you have a springy dough, pulling it to make 'meaty' strands.
Bring a large pan of stock to a boil, break the dough into palm-sized chunks, add to the stock, reduce the heat, and simmer for around 30 minutes.
Remove the pan from the heat, allow the seitan to cool in the stock to room temperature, then place into an airtight container, along with enough of the stock to cover. Place in the fridge for at least five hours - preferably overnight - to firm up.
When ready to glaze, remove the seitan from the fridge, and cut into slices.
Heat a large skillet over a medium heat, and fry the seitan in a little oil until lightly browned on both sides.
Add the BBQ sauce ingredients to the skillet, and stir continually, until the sauce has coated all of the seitan pieces, and is beginning to thicken.
If you can't get Dorsetshire Sauce, you can use vegan Worcestershire instead.
The seitan isn't heavily-flavoured, instead it relies on the BBQ sauce for its tastiness.