In the film 'Mary Poppins', how much was a bag of birdseed?

'Feed the Birds' is a song written by Richard and Robert Sherman for the 1964 film 'Mary Poppins'. The song is about an old woman, known as the 'Bird Woman', who sits on the steps of St Paul's Cathedral in London, selling bags of birdseed for tuppence (or twopence), so that passersby can feed birds, mostly pigeons, on the streets.

In the movie, Jane and John's nanny, Mary Poppins (Julie Andrews), sings the song about the Bird Woman one evening before they go to bed. The next day, their father takes them to the bank where they pass the Bird Woman. He discourages the children from giving money to the woman, insisting the money would be much better in a bank account. The Bird Woman was played by Academy Award winner Jane Darwell (1879-1967), who appeared in over 100 films during her career.

Selling birdseed in London was common during Victorian and Edwardian times. Seed vendors usually frequented Trafalgar Square, which opened in 1844. The square quickly grew a reputation for the number of feral pigeons that frequented the area. The selling of birdseed was eventually stopped in 2001 by which time the pigeon population had grown to such an extent that it was considered a health hazard. People continued to feed the birds with food brought from home until the Mayor of London issued an official ban in 2003.