600th post

In days of old
When knights were bold
The story's told
Of Lancelot.

Before he was Ian Chesterton in Doctor Who, William Russell played Sir Lancelot in the TV series The Adventures of Sir Lancelot. In it, he was so cool that Patrick McGoohan, one of the coolest mannys to have ever lived and been on TV, was a guest in his show.

This was in 1956 ("days of old" indeed), so it was made before Patrick McGoohan was even in Danger Man.