By the 1900s the whole line was under pressure from overcrowding. The populations of areas along the line, particularly at Hornsey, Highgate, Muswell Hill, and Finchley, had increased considerably with the rapid Victorian expansion of London, but the GNR service had not been expanded to cope. The line was also congested with goods traffic, mostly coal and building materials. By 1903 the morning trains from Barnet were full by the time they arrived at East Finchley. As the doors of the compartments in the carriages were in those days locked with aid of a simple square key, some passengers took to purchasing these keys from local ironmongers, and locking the doors from the inside. It was not unknown for harsh words and even, on odd occasions, for blows to be exchanged.