Tube logo 'a great British brand'
10 January 2013 Last updated at 19:12 GMT
The Underground logo has become one of the most instantly recognisable symbols of London.
As the Tube celebrates 150 years in operation it is now hailed as a great British brand with official merchandise and licensed products bringing in £5m a year.
But how did the Underground brand become so successful? BBC London's Nick Beake meets Michael Czerwinski of the Design Museum and Michael Walton of the London Transport Museum in Covent Garden.
Footage courtesy of British Pathe.