Thorn Alpha 1

My first lantern was removed on the 26th March 2002 from column number 24199 (Blagreaves Lane, Derby) due to faulty control gear. The replacement lantern was an Alpha 4 of the same wattage. The lantern was brought round a day later; however, I wasn't in at the time, and so it was kept hidden until Easter Monday (1st April - appropriately!), when it was given as a late 'Easter egg'! Being my first lantern, and a gearless one at that, I was unsure as to what gear was required, let alone how to wire it up, so I had the gear fitted professionally, and on the 26th June, the wiring was completed, and I, at last, could run my first lantern properly!

The Alpha 1 is, and will always be one of my favourite lanterns - it looked nothing like anything that had been produced before when it was first launched in 1955, to a design put forward by Mr Richard Stevens, and nothing like it was ever tried again - the Revo Sol d'Or came close, but still does not match the quality or simplicity of the Thorn lantern. In 1958 the lantern won a prestigious design award at Milan, as it was the first hermetically sealed and injection moulded optical system for a road lantern. Only in the early 1990s was production of the lantern discontinued - an excellent lifetime for a design that was as groundbreaking then as it was over 30 years previously. The example seen here is likely to be a 1970s' version.

The following is the inventory record for this installation. This record is as it was in 1997, when Derby City Council took control of its own street lighting repairs from the County Council. Therefore, any changes made after this date are not known.

Unique Number: 24199 Location: O/S NO 235
Postcode: DE3 7BT Road: BLAGREAVES LN
Road Number: C171 Parish: LITTLEOVER
Sequence Number: 39 Patrol: Y07
Lamp Type: SXP3 Wattage: 90 Watt Control Type: PE1E
Lamps/Lantern: 1 Lanterns/Unit: 1 Control Setting: 4
Lantern Type: SE Lantern Manuf:   Control Gear:  
Height: 8  m Support Type: TS TUBULAR STEEL - PAINTED
Bracket Proj'n.:    m Support Finish: P PAINTED COL/SIGN/PILL/GANTRY
Bracket Type:   U/G or O/H: U UNDERGROUND
Board Code: E76 Status Code: 0 USUAL / NORMAL
Service Owner: T Is this lamp/sign an Isolation Point ?: N
EB Order number:      
No-supply sheet: 0 Isol Pt:   / Circuit:   / Seq:  

Vanity strikes as I am pictured with my newly-acquired toy in 2002.


The Alpha 1 resting on my top shelf (where else?). The metal object just about visible under the casting is the 'Opticell' securing toggle. It used to fit completely into the slot, but after I sprayed it with WD 40, it hasn't gone back in completely. Before the toggle was sprayed, it was quite a job to fit back into place and I was concerned that excessive force could have bent it out of shape.

The Alpha 1 from above. Prior to acquisition, I didn't realise that a baffle plate is situated above the lamp, in order to reduce the amount of light being beamed upwards out of the lantern. The lantern is held on the bracket with three equally-spaced grub screws; however, after years of being exposed to the outdoors, these are now jammed and cannot be removed. In fact, the remains of an Allen key can still be seen in the slot on this side of the lantern; quite how the lantern was removed from the bracket without needing to be hammered off (resulting in possible damage to the rear section) is a mystery!


Turning the lantern over reveals the Opticell securing toggle fixed into the underside of the shoe. Although the Opticell looks spotless internally, there are a few flecks of dust towards the end of it. These cannot be removed unless the Opticell was split open (which is certainly not advised!). This is a 'lucky' Alpha 1 - very few have such clean Opticells nowadays - most have a nice pool of gradually greening rainwater below the lamp, owing to the seal at the 'open' end having perished.


With the Opticell having been unclipped from the rear casting, the secret behind the Alpha 1's sealed lamp area is revealed.

An aluminium plug fits over the narrow open end of the Opticell, and is secured with two clips. The lampholder wiring passes through a sleeve, which ensures that the cable entry hole is sealed too.

Inside the casting is a small plate that supports the supply connector block, a cable restraint for the lampholder wiring, and (ordinarily, but removed in this view) a cable clamp for the incoming cable/s - there is space for a second connector block to be fitted, for use in terminating any photocell cables that exist. As the photocell was situated on top of the bracket with these installations, the casting has not been drilled to accommodate such a device.

As previously mentioned, this was my first lantern, and back then I didn't know too much about control gear, so I had someone to fit and wire gear up for me. The components (L-R) are the Ignitor, Ballast and Capacitor. Just look at all those wires! Anyone fancy spaghetti?

The Alpha 1 at full power. The support for the lamp can just be seen. The refractors on the sides of the Opticell do a good job in directing most of the light downwards.


Twenty years after acquiring the Alpha 1, I decided, finally, that it deserved to be given a more 'conventional' means of installation, and so, it was fitted to a wall bracket on Thursday, 31st March 2022 - yes; a day before the 20th anniversary of my discovering that an extra Easter present was waiting for me! The two 'side' grub screws were jammed solid (as mentioned earlier, one had the remains of a broken Allen key left inside it!), but thankfully, the grub screw on the underside of the canopy was coaxed semi-free, and provided sufficient grip to anchor the lantern to the bracket.

The new bracket allowed the lantern to be seen from far more angles than had been possible when it resided on the shelf.

This view allows the internal baffle plate above the lamp to be seen. The identification label is affixed to this - it includes information that the lamp area is sealed to IP 54 (quite low by modern standards, but much higher than any other contemporary lantern could offer in the 1950s), while the luminaire carries an overall rating of IP 23.

Prior to installing the lantern, I recreated the picture from 2002 seen above - this is what devoting twenty years of your life to collecting street lights does for you - it isn't pretty (physically or mentally)!

Lantern warm-up video:

The column, which had previously supported the Alpha 1, 24199, was itself scheduled to be replaced as part of the Derby Street Lighting PFI. The following photographs were taken on Sunday, 21st September 2008.

A photograph taken in 1981 of Blagreaves Lane (a little further up the road) reveals the Alpha 1s when they reigned supreme; click here to see it. Thus, the lantern that entered my Collection was (at least) twenty-one years old upon acquisition.

| Thorn Beta 5




© 2002 - English Street Lights Online