London Underground 150 year anniversary stamps

On the 9 January 1863 London Underground, the World's first underground transport system, opened and the first underground train took passengers on a 3.5 mile ride from Paddington to Farringdon.

To celebrate this 150 year milestone Royal Mail have released a set of 6 commemorative stamps (above) that illustrate the tube's timeline with lithographs, illustrations and photographs. They also give a nod to the design of the iconic tube map.

However, it's these miniature stamps each showing 3 classic London Underground advertising posters that I found the most interesting/inspiring...

Images copyright Royal Mail.
Stamps designed by Hat-Trick.
Miniature stamp sheets designed by NB Studio.