So, I'm reading Churchill's History of the English-Speaking Peoples (a bit dated, but, as usual, very well written), and I came across an interesting fact. King Offa of Mercia (the one who built Offa's Dyke, for you Brits out there) minted very nice coinage. He wanted to have very good coinage indeed, and to that end got dies for the best coins in the world -- Abbasid dinars, which were retooled to mint coins with his name on them (REX OFFA). However, the coins are still very good copies of the dinars, right down to the squiggles on the back; so his coinage also proclaims that there is no god but God and that Muhammad is his prophet.
Any way of making the kingdom of Mercia actually Islamic in the late 9th century? Bonus points if your answer does not contain the word "Tours".