An historic mail train service which runs under London will cease deliveries next week.
Royal Mail want to find a new commercial use for the service
Royal Mail is axing the Mail Rail service, which runs from west to east London, because it says it is no longer viable.
In its heyday, the 75-year-old service carried four million letters a day and stopped at nine stations between Paddington and Whitechapel.
But changes to the distribution of mail and a massive drop in postage in the city mean it is too expensive to run, says Royal Mail.
A new commercial use is being sought for the service.
Patrick Breen, of Royal Mail, said the closure of the service would be a "sad day" for those who had worked on it.
The idea of an underground rail service for London was first mooted in 1855 by the then secretary to the Post Office, Rowland Hill.
Although trials were conducted in small tunnels, the Post Office abandoned the scheme until early in the next century. It was eventually given the go-ahead by the government in 1913.
The trains run in tunnels under the Tube network
The outbreak of World War I halted construction and the little tunnels were used to store art treasures from major London galleries, such as the Tate and the National Portrait Gallery,
Work began on the tunnels again in 1923 and the first trains started delivery four years later - under the banner of the Post Office Underground Railway.
It became Mail Rail on the service's 60th anniversary, shortly after the old stock was replaced with 34 new trains.
Currently, Mail Rail runs along a 37km route between Paddington in west London and Whitechapel in the East End, and is staffed by 76 postal workers.
Last month, the London Assembly said the service should be kept open to reduce traffic above ground.
A report by the assembly said more action was needed to return the line to full service and avoid "leaving a unique part of London's heritage to gather dust".
But a Royal Mail spokesman said the service cost more than four times as much as the alternative above ground.
He said it would not be left to gather dust as a specialist team would keep it in good working order.
Patrick Breen, from Royal Mail told BBC News on Friday: "The service was no longer doing what it was supposed to do."