The development of lanterns continued through the 1930s and accelerated when it was determined that the lamp’s brightness and its long length made it less susceptible to glare. Lanterns with bare bulbs suspended over an overhead reflector (the so-called "seagull" lanterns) quickly followed. Glass manufacturers were initially slow as the first plate refractors for low pressure sodium lamps didn’t appear until the end of the decade.

The advantages and disadvantages of low pressure sodium were readily debated, especially when an alternative (the medium and high pressure mercury discharge lamp) was also available. The monochromatic light was considered especially useful for arterial and traffic routes, the lamp’s shape cast a wide beam across the road surface, the light was also considered more penetrating in foggy conditions and it was the most efficient light source being manufactured. However, the light was also considered inappropriate for high streets, promenades, civic areas and residential streets and so some lighting engineers restricted its use to traffic routes only. Therefore low pressure sodium became known as "the drivers’ lamp."

The arrival of plate glass refractors resulted in large lanterns made of metal frames enclosing heavy glass sheets. These bulky lanterns continued to be made into the 1950s until being usurped by lanterns with plastic bowls and machined or moulded plastic refractor plates. The lanterns were still large; the size dictated by the bulky control gear, but their design and construction was becoming simpler.

The 1950s and 1960s saw huge improvements in the construction and efficacy of low pressure sodium. Early two-piece designs (dubbed SO) were replaced by the one-piece, more efficient integral design (called the SOI). The development of linear sodium (SLI) broke the one hundred lumens per watt barrier, lead to a radical rewriting of the British Standards of street lighting and prompted the development of new families of streamlined lanterns. But it wasn’t until the arrival of a new heat-reflecting technology (called SOX) that a cheap family of extremely efficient bulbs became available.

The energy crisis of the 1970s saw a rethink in street lighting and lamp efficiency became dominant when fuel was both in short supply and expensive. This saw the large scale removal of colour corrected high pressure mercury, fluorescent and ancient tungsten lamps by low pressure sodium replacements. The old arguments that the smoky-orange lamps were inappropriate for residential areas no longer applied. By the end of the 1980s, low pressure sodium was the dominant street lighting lamp used in the UK.

The use of low pressure sodium came under scrutiny again. High pressure sodium, finally developed as a viable technology in the 1960s, was coming of age and offered a compromise of slightly less efficacy with better colour rendering. Questions were being asked about the physiology of the eye and visual adaptation under low lighting levels; previously the wavelength of low pressure sodium had been deemed the most suitable, but research now suggested that the eye responded better to white light. Concerns were raised about light pollution and the low pressure sodium lamp was seen to be the chief culprit (although it was more to do with older non-cutoff and semi-cutoff optical designs rather than the lamp itself).

By the turn of the century, the age of low pressure sodium was seen as coming to an end. Research in white light technologies, especially metal halide and a renewed interest in compact fluorescent coupled with the advantages of using white light at low lighting levels, saw the end of the low pressure sodium lamp’s dominance. Its use was discouraged in the specifications, lantern manufacturers started to wind down their production and bulb manufacturers followed suit.

By the end of the first decade of the 2000s, low pressure sodium was in stark decline, and less and less of the UK’s streets were being lit by its characteristic orange glow.

Name: Thorn Beta 8
Date: Early 1960s - Early 1980s
Dimensions: Length: 22.75", Width: 9.5", Height: 7.25"
Light Distibution: Semi Cut-Off (BS 1788:1964)
Lamp: 35-55W SOX

The lineage of the Thorn Alpha Eight can be traced back to the later years of British Thomson Houston (BTH) who manufactured the popular range of Amber lanterns. The design of the Amber lantern changed over the years (although it could be argued that BTH simply called their existing low pressure sodium lantern the "Amber" regardless of appearance) until the rounded "boxy" bowl was replaced by an angled, tapered version. By this time, BTH had been assimilated into AEI and the linear sodium lamp had been developed. The smaller wattage lantern was adapted to take this new bulb, along with a subtle renaming, and so became known as the Junior Amberline lantern. Further manoeuvring within the lighting industry saw Thorn take an interest in AEI’s lamps and lighting operation, and after purchasing a stake in the company, Thorn started selling the lantern under their "Atlas" moniker as the Atlas Beta Eight. By the end of the 1960s, Thorn purchased the entire operation, and the lantern continued as the Beta Eight (although stickers inside bore both the “Beta Eight” and “Junior Amberline” names). It remained in the catalogue as Thorn’s 55W low pressure sodium lantern (although the Alpha One and Alpha Ten could accept this wattage, they were seen as Group A lanterns). It was a fairly popular lantern, but large for its size, and most lighting engineers chose more streamlined offerings from other manufacturers. By the early 1980s, Thorn began to rationalise its range, and the lantern was discontinued in preference to the new Beta Two.

The base of the gear tray was painted white to act as a secondary optical system, reflecting light cast above the horizontal back down to the road surface.

The exterior of the bowl is smooth to facilitate easy cleaning.

Originally standing somewhere in the Derby area, this Thorn Beta 8 was probably installed in the late 1960s/early 1970s as it also bares its original name, the AEI Junior Amberline.