SECR F1 class
Type and origin Power type Steam Designer Harry Wainwright Builder Ashford Works Rebuild date 1903–1919 Number rebuilt 76
Specifications Configuration: ​  • Whyte 4-4-0  • UIC 2′B Gauge 4 ft 8+1⁄2 in (1,435 mm) Driver dia. 7 ft 0 in (2.134 m) Loco weight 45.1 long tons (45.8 t) Fuel type Coal Boiler pressure 170 psi (1.17 MPa) Cylinders Two, inside Cylinder size 18 in × 26 in (457 mm × 660 mm) Valve gear Stephenson
Performance figures Tractive effort 14,491 lbf (64.5 kN)
Career Operators South Eastern and Chatham Railway → Southern Railway → Southern Region of British Railways Class SECR/SR: F1 Number in class 1 January 1923: 75 Nicknames Jumbo Withdrawn 1920–1949 Disposition All scrapped

The SECR F1 class was a series of 4-4-0 steam locomotives operated by the South Eastern and Chatham Railway. These locomotives were rebuilt from older Stirling F class locomotives by Harry Wainwright between 1903 and 1919.^[1]

Seventy-six locomotives were rebuilt, and 75 survived into Southern Railway (SR) ownership as of 1 January 1923. They were assigned random numbers ranging between 2 and 250. Nine locomotives survived into British Railways (BR) ownership in 1948.^[2] Numbers of these nine were:

• In August 1926, a F1 class locomotive overran buffers at London Bridge and crashed into a brewery.^[3]
• On 19 August 1928 A148 was deliberately crashed into a lorry at Lasham, between Basingstoke and Alton, for the film 'the Wrecker'. The remains were cut up on site.^[4]