Just noticed your index definition of brown sauce, chris, & it's lamentable, frankly.
The UK's most popular brand of brown sauce is HP sauce. The HP standing for Houses of Parliament. It has a picture of them on the label to prove the point.
Sad to say, I have a hot bacon butty & bottle of HP before me, & the ingredients are, in descending order of contents, & I quote from the label:
Malt vinegar (from Barley)
Modified maize starch
And it has the Royal Seal of Approval. So the Royal Family have it on their bacon butties.
All other brown sauces simply don't taste as good.
It must be used in Extremely Small Measures on your bacon butties, English breakfast (never on burgers, as it's too strong), unlike tomato ketchup, as it's extremely pungent, concentrated & tangy, in a brown sort of way.
I once recommended HP brown sauce as an addition to a fry-up English breakfast to a Canadian lady of my cyber acquaintance, so she found some in Toronto.
I forgot to mention that you should just put a little bit on the side of your plate, so she poured a whole bottle over her kids' breakfast fry-ups.
She wasn't best pleased, but I think the kids liked it, as they got a day off school as a result of tamarind palate-overload.
it's also good with shepherds pie, corned beef hash, sometimes with chips if you've a strong constitution, pies, & Heinz baked beans.
But in small quantities.
My bacon butty has gone cold now, so I'll get the wife to microwave it for me & add a Small Amount of HP sauce to it.
I may be bonkers but at least I'm British.