It wasn’t until the early 1960s that General Electric (GE) cracked the problems, closely followed by the GEC and Philips. A prototype high pressure sodium lamp was exhibited at the APLE's annual conference in 1963, but it wasn’t until 1966 that the GEC erected an experimental installation along East Lane, Wembley (which, incidentally, also saw the first experimental medium-pressure mercury installation over thirty years before).

The first commercial installation in the UK was erected along the Southend ring road, but it was the City Of London who gained the most recognition by beginning a radial upgrading of all their lighting to high pressure sodium in 1967. As the early HPS bulbs were designed to be retrofitted into existing mercury installations, the lanterns chosen by the City Of London were slightly modified versions of existing mercury lanterns.

The first true HPS lanterns (designed from scratch with the new light source in mind) appeared in the late 1960s and early 1970s. All these lanterns utilised a cross-over design: whilst this was an adaption of existing mercury lanterns, it also moved the lamp up into the lantern’s canopy (where it could not be directly viewed by drivers, thus minimalising the glare) and allowed designs to cater for both cut-off and semi-cut-off.

Wider adoption of high pressure sodium was stalled by the energy crisis, as it couldn’t match the efficiency of its low pressure sodium brother. Councils, believing in the simple maximum lumens per watt paradigm, replaced existing tungsten, mercury and fluorescent schemes by low pressure sodium. So it wasn’t until the 1990s that HPS started appearing in greater quantities.

With its efficiency between high pressure mercury and low pressure sodium, HPS became even more attractive when LPS was finally exorcised from the British Standards of street lighting (as it didn't provide an adequate colour rendering). However, it didn't remain as first choice for new and replacement lighting schemes for long. Renewed interest in fluorescent (from compact fluorescent sources), the emergence of affordable metal halide and the possible introduction of LED have all questioned the automatic selection of high pressure sodium for schemes.

Therefore by the end of the first decade of the new century, high pressure sodium’s position as the natural choice for street lighting was coming under pressure.

Name: Davis Starline GR70
Date: Mid 1970s -
Dimensions: Length: 57cm, Width: 27.2cm, Depth: 19cm
Light Distibution: Cut-Off (BS 4533 Part 2)
Lamp: 50-70W SON

It isn’t known which company designed this lantern. It was either one of ELECO’s final designs, or was one of the first by DAVIS, who took over the ELECO range when it became amalgamated as part of the ELECO Holdings companies. It was extremely typical of the new range of lanterns being designed specifically for high pressure sodium and shared many design characteristics with competitor products such as the Beta 79 by Thorn and the Z5530 range by the GEC i.e. a cut-off lantern with cross-over optics and a separation of the lamp and gear compartments. Again, like many of its competitors, the lantern could take a variety of bulb options (including high pressure mercury) and it obsoleted many lanterns in the company’s range. However, the single clip wasn’t particularly robust and failed to keep the seal between the bowl and canopy dustproof. Also the single Philips screw holding the gear compartment secure was also prone to rusting and/or losing its thread. Therefore it wasn’t surprising when a successor lantern appeared in the early 1980s: the DAVIS IP65 Lantern fixed these design errors by employing two side clips and a bowl which enclosed the entire length of the lantern.

The secondary optical system comprises a white plastic over-reflector mounted above the bulb which reflects light emitted above the bulb back towards the street surface. It is particularly mean as the piece of plastic simply sits above the bulb and doesn’t fit into the entire canopy roof.

When opened, the cover plate swings open and all the gear is mounted on its opposite site. Three components are usually screwed to the cover plate: the main lamp choke, a power correction capacitor and an ignitor.

facing profile This lantern was originally installed somewhere in Devon. The DAVIS Starline GR70 and its successor IP65 Lantern were both popular in the county.

front profile The bowl is held in position by a single plastic clip.

trailing profile After years in service, the GRP compound had started to break down slightly, the adhesive losing its grip and leaving the exterior of the lantern slightly "furry" to the touch. These glass fibres would then break off and attach themselves to clothing and/or exposed flesh causing a nasty, itchy rash. As the lantern was high off the ground whilst in service then this normally wouldn't be a problem; but some lanterns were painted whilst in service to halt this gradual breakdown.

canopy The side-walls of the canopy are completely flat and smooth; there are no rims or extrusions for hinges etc. This is one way of identifying this lantern.

logo The company's logo is boldly embossed on the road-side of the lantern.

pedestrian view This classic view clearly shows the two reflectors positioned either side of the bowl to produce the cut-off distribution.

vertical The bowl is simply clear and doesn't carry any additional refractors.

interior #1 The secondary optical system comprises a simple white plastic sheet screwed into the canopy of the lantern. The size of this over-reflector is particularly mean and doesn't cover the entire canopy's roof.

interior #2 The interior of the gear compartment was quite dirty. Not surprising giving the number of years of service and the inadequacy of a single Philips screw (which had lost its thread and required pulling out with a pair of pliers). I believe the original gear is still in-situ: a Philips BSN 70L 34 for 70W SON; a Cambridge Capacitors L10C50 capacator rated at 10uF; and an ignitor (unidentified as the sticker had gone). The lantern also includes the largest terminal strip blocks I've ever seen in any lantern.

This lantern originally stood somewhere in the Devon area, a swap with fellow collector Davy Warren.