In October 1934, the 250 was already a T-operated single-deck route from Romford to Epping, with a partner 250^A, which diverged at Passingford Bridge for Ongar.  This latter became the 123 when double-decked in December 1936.  As would be expected in such sparsely populated country, the routes were infrequent even then, with about six through journeys each day on each.  At that time, the southern terminus was Rainham Road Gordon Avenue, just south of Roneo Corner.

By 1948, the route had been shortened to Romford Station.  It was that October that the first four of the second batch of TDs went to Hornchurch for the 250.  One 1T1 was retained as a spare and for the peak - Sunday - service.

In May 1950, the route was re-extended to Hornchurch Garage, an arrangement that was to stand (except for Sundays in that first winter) for 23 years.  The next change was the re-allocation of the TDs to Romford North Street garage, at its opening on 12 August 1953.

In November 1958, the route was diverted south of Epping via Ivychimneys Road, opening up new bus territory, instead of following the 20 to Epping Town, and for seven weeks in February 1959, the route was extended M-F peaks to Corbets Tey.

Conversion to RF operation came a few months later, in July 1959, by which time it was the only single-deck route operating in the Romford area.  The route was obviously suited to OMO conversion, and it was one of the first four in November 1964.

Further small route changes occurred in the early 70s, with the route cut back from Hornchurch to Romford Station in June 1973 (but the frequency to Passingford Bridge increased to cover shorts on RT-operated 175) and extended in Epping to St Margaret's Hospital in November 1974. 

The route was finally converted to BL operation in April 1976, lasting less than eight months before discontinuation in January 1977.  The long section between Colliers Row and Epping was added to the 247, making it then the longest route in London, only to be finally withdrawn in July 1981.