SIR Lenny Henry. OBE. I actually didn’t know he was knighted. :P
Among things, this comedian founded Comic Relief (the source of this cameo and a dozen other Doctor Who appearances on the event over the years, including the infamous Rowan Atkinson edition) in 1985. He is arguably the most prominent black British actor of the previous century, the equivalent of Eddie Murphy or Chris Rock in their day.
Pretty much any living British person will know him, love him or hate him. I’m Canadian, so I knew of him plenty but mostly through other shows. Many of us saw him recently as the elder not-Hobbit in the recent “Lord of the Rings: The Rings of Power” on Amazon.
Mark