Employees at work sorting letters at the Royal Mail Mount Pleasant Sorting Office; c 1965

The Mount Pleasant Sorting Office in Clerkenwell was thought to be the largest in the world covering an area of 7.5 acres. A system of post codes was introduced across the country to ensure that mail could be sorted efficiently and effectively. Trials in Norwich in 1957 were successful and by 1974 the entire country had been coded. The first fully automatic sorting machines were not introduced until 1979 and until this date sorting had to be completed by hand. This photograph was taken by Henry Grant on a visit to the Mount Pleasant sorting office organised by the National Association of Youth Clubs.