On 11 June 1933 CMB took over the route as part of the Hong Kong Island bus service franchise, and given the number 4.

Service was resumed on 16 April 1946 between Central Ferry Piers and Queen Mary Hospital, with initially only two buses running and a frequency of one hour per bus, to be increased gradually.

As the population of Wah Fu increased, an express service was implemented in 1971, which faced delays caused congestion problems along Des Voeux Road West.

During the morning peak of Mondays to Saturdays, services would operate from Wah Fu (South) as a circular bus route to Central.

It also skips Sheung Wan and most of Sai Ying Pun on its return journey in morning peak hours.