Multiple people have suggested this here. It seems very strange to me, since Shakespeare is one of the most famous Englishmen of the Elizabethan era, and Milton was politically active 50+ years later during the English Civil War.
A surprising number of English people don't know that there was an English Civil War. When you've got a thousand years of continuous history to pack in, Oliver Cromwell ends up being kind of a footnote.
Maybe if it had occurred before Shakespeare, instead of after, he could have written a cycle of plays about it, and we'd remember it as well as the Wars of the Roses. But as it is, English schoolchildren forget it as soon as class is over... and I suspect the rest of the UK cares even less.
