Who designed this Minton tile..?

Nobody knows everything, and you ought to run away from anyone who says they do. I know very little about tiles, it’s a very specialist market. But a specialist market that is growing in size and appeal as more choose to use antique tiles in fireplaces or hallways or, in fact, all over the house.
Our hallway is floored with some Victorian terracotta and sky blue tiles that look very much the bee’s knees, and came from Leominster Reclamation. Away from the architectural side of tiles, I’ve always admired single tiles displayed in plain, thick wooden frames and hung on a wall.
So the week before last, for more reasons than its visual appeal, I bid on the Victorian tile shown here at an auction I attended. And won it.
My question is, who designed it? And when?
The back of the tile has nine ridges and bears some recently applied paper labels reading ‘Minton Prosser’s Patent / This tile probably exhibited with Pugin’s Great Stove / Great Exhibition 1851 / Hence damage from feet‘. Interesting – but probably largely not to be trusted. Research has shown me that it was indeed not a part of A.W.N. Pugin‘s Great Stove, as it’s completely different, and my Antiques Roadshow colleague Paul Atterbury has kindly confirmed that Pugin didn’t design it. I can’t find any images of the Medieval Court, where the Great Stove stood, which show any other tiles. It would also follow that it wasn’t even in that room, as the Medieval Court was designed by Pugin.
Hawk-eyed Brian Greenfield very kindly emailed me to point out the fact that the back is moulded with wording for both Minton and Prosser, so that gives me a perfect start – if I can gain access to the Minton Archive (which I believe is part of the threatened Wedgwood Collection), I should be able to find the designer’s name. Richard Prosser was a Birmingham-based engineer and inventor, and lived from 1804-54 according to a descendant.
It measures 12.5cm high, 12.9cm wide, and 2.2cm widest, including a ridge on the back and the moulded low relief pattern on the front. There’s a fair bit of wear to the low relief pattern, referred to by the labels, and the cobalt blue glaze.
It has stumped three other people who I thought might know but, if you know, please contact me by clicking here. I’d be delighted to learn more about what I have bought!
Thank you.