Indeed -pre woke - a time when a spade was called a shovel & used to colloquially be friendly to West Indians who never wore badges proclaiming their island of origin & so were collectively called Spades because the most common thing was the spade used to shovel black coal.
Your resources may reveal other reasons for the term Len but who can ever forget the black shovel skit. Sadly couldn't find it but enjoyed this one:

@LenHazell53 in a class with my oft quotes on "t'life living in t'gutter in a soggy shoebox". I'd forgotten how the rain slashes down until recently watching a couple of UK shows including the one above.