Yes, it is. *thirty lashes with a wet strand of udon noodle*Hi Phyllis –
No. I compared the ingredients, quite different.
HP: tomato base, malt and spirit vinegar, molasses, dates, cornflour, rye flour, salt, spices and tamarind.
57: tomato base, vinegar, apples, and raisins.
Having looked, it's closest relative are your 'steak sauces', but they differ. A1 Sauce, which I think you have over there, is actually from a recipe developed by the same man who developed HP Sauce, a grocer in Nottingham, UK.
I rewatched the episode of Grounded Travels where they talked about having an Amtrack flatiron steak, and the staff included a bottle of A1 steak sauce (much to the delight of the couple!)
Phyllis Sidhe_Uaine