The Leicester Mystery Stone

This 60-pound (27 kg) piece of carved sandstone turned up in a garden is Leicester, England. It was purchased by TV presenter James Balme, who is fascinated by the carving and has been broadcasting the image over twitter, asking if anyone knows what it is or what it means. Balme thinks it is Anglo-Saxon, which seems like a good guess to me. But I can't make out any of the animals, faces or other elements that Anglo-Saxon artists sometimes concealed in abstract-looking designs.