As London's Blue Plaque scheme celebrates 150 years, we wanted to point out some of the quirks of the project.
Did you know four blue plaques feature a different font to the others?
They are, of course, the plaques commemorating the pioneers working for London's transport system around the time Edward Johnston developed his iconic typeface.
Johnston's eponymous font is also celebrating an anniversary this year: it's 100 years since the typeface was introduced onto London's transport system.
The other men commemorated with blue plaques featuring the Johnston font are Harry Beck, the man behind the Tube Map...
...Frank Pick, the chief executive of London Transport in the 1930s, a man with unrivalled flair for design-management...
...and their boss, Lord Albert Stanley Ashfield, the first chairman of London Transport.
The blue plaque scheme is open for nominations. Who do you think should get a blue plaque?