The display card reads -
'These boots were worn in the 1896 production of Richard III at the Lyceum Theatre. The heel of the left boot was raised to give him an artificial limp, the difference in height carefully masked from the audience by a panel of red suede. The Times critic wrote 'Irving's Richard is the most Satanic character I have ever seen on the stage.'.
It reminds me of the story of Dustin Hoffman wearing a stone inside his shoe to maintain a consistant limp throughout the filming of Midnight Cowboy and goes to show that not much is new.