SEE SL8

Contents

• Overview
  • General data
• Lines
• Can be confused with
• Tower forms
  • Examples
  • Tower views
    • Terminal
• Tower details
• Locations
  • Cheddington
• See also

Overview

SEE SL8 was the contract for the 33 kV overhead line between Rayleigh and Southend-on-Sea, Essex. A short section of this line remains leading up to Fleethall substation.

Only a single drawing has been recovered, for the unique gantry-style terminal tower. The drawing bears the following annotation:

Also applicable to S.L.9 Luton and Aylesbury - see M & M letter 17/1/’42 - [unclear code]

The image quality is poor. “M & M” is uncertain but almost certainly refers to Merz and McLellan. “S.L.9” is also unclear, but is a reasonable interpretation. There is a line between Luton and Aylesbury that uses the same tower suite as that found at Fleet Hall and in so far the only discovered depiction of a tower at Southend.

There is no readable date on the drawing, but the drawing number of 2706C would appear to put it before SEE PL7 (1938) with 2800-series drawing numbers. The SL9 annotation and wartime use all date to 1942. The surprisingly low drawing number (6) and the wording “Luton and Aylesbury” (not “Luton to Aylesbury”) carries a suggestion that contract SL8 was just the terminal tower. For now, SEE SL8 is being taken to be the entire tower suite.

The terminal tower was used on other SEE lines (with different tower types) where sections of line were buried below new RAF airfields during World War 2.

SEE SL8 (Rayleigh to Southend) is stated to be 33 kV, but the towers are built to 66 kV clearances, and the terminal tower at Colchester Grid Substation is insulated to 66 kV.

Very similar towers were used for NWE SL7.

General data

Lines

Known lines:

• Rayleigh–Southend, Essex, much of which is now demolished; appears to be SEE SL8
• Luton–Aylesbury, Bedfordshire–Buckinghamshire; suggested to be SEE SL9

The terminal towers can also be found on other lines:

• At Long Marston and Cheddington, either side of the undergrounded section of the Luton–Aylesbury (Bedfordshire to Buckinghamshire) line that made way for the former RAF Cheddington that opened March 1942
• The line between Colchester and Coggeshall, with unidentified towers:
  • Each end (PYF1 and PYF5) of the short segment outside Colchester Grid Substation
  • Each end of the undergrounded section that made way for RAF Birch, Essex, opened 1942

Can be confused with

• NWE SL7

Tower forms

The following diagram is shown to scale at 12 pixels per metre.

The designations of the towers are unknown. The angle towers appear to be 10°, 30° and 60°. The preliminary diagrams below (based on Google Street View and photographs taken in Cheddington) are scaled to crossarm spacing of 8 foot 6 with ground clearance of 40 foot on the angle towers, as per the terminal tower and consistent with towers of a similar age. The line tower ground clearance is a compromise between other types at 44 feet.

Examples

Tower views

Terminal

All photos are from pylon hunt 43, 12th July 2025. This is the start of the seemingly SEE SL9 line from Luton to Aylesbury.

Tower details

Locations

Cheddington

Photos from pylon hunt 32, 7th September 2024. This is the start of an undergrounded section, between Cheddington and Long Marston, of the Watshams SEE SL3-like line between Luton and Aylesbury. The tower is partially obscured from view and the weather on the day was not great.

See also

• D10 (?) tower, Fleet Hall (Geograph)
• D30 (?) tower, Southend (Geograph)