British Rail Class 33 (BRCW Type 3) — the "Crompton" that made the Southern Region's diesel era work

If the British diesel story has its celebrities, the British Rail Class 33 is something better: a working professional. Not the biggest, not the fastest, not the most glamorous—and yet so perfectly matched to its patch of railway that it became inseparable from it. Built for the British Rail Southern Region, the Class 33 was a Bo-Bo diesel-electric locomotive designed for the awkward reality of a network part-electrified, part-not, and full of the kind of varied traffic that doesn't care what a locomotive was supposed to do.

They were known formally as the BRCW Type 3, and informally as "Cromptons"—a nickname that stuck so hard it became the class's second name. They hauled summer Saturday holiday trains, winter freight, parcels, engineers' trains, boat-train portions, and just about anything else that needed a dependable Type 3 with electric train heating. They were also, in a very Southern way, adapted into odd specialisms: some became push-pull locomotives for the Bournemouth line; a small group were narrowed to fit the tight tunnels of the Hastings line. A class that began as a standard modernisation purchase ended up wearing several very particular jobs.

Why the Southern Region ordered them

The Class 33 is often described as a diesel ordered "because of electrification", which sounds like a contradiction until you picture the Southern Region in the late 1950s. The big plan—approved in the era of the modernisation programme—was to extend third-rail electrification across major routes. But a fully electrified Southern was still a future goal, and plenty of secondary routes, freight flows, and seasonal passenger work would remain non-electrified or unevenly covered. The region needed a locomotive that could cover that mixed world: passenger trains at reasonable speeds, vans and parcels, and freight, all while fitting within a busy passenger railway that prided itself on acceleration, reliability, and flexibility.

So the Southern Region wanted a Type 3—more powerful than earlier Type 2s, but not a heavy Type 4—and wanted it in a form that suited their operating pattern. One key point was heating. Steam heating boilers were a reliability pain, and the Southern was already deeply invested in electric systems and the practical logic of electric train heating (ETH). A locomotive designed around ETH, without a temperamental steam boiler taking up space and maintenance hours, was a very Southern solution.

The result was an order for a locomotive with 1,550 bhp, an 85 mph maximum speed, and a layout that looked like a slightly more assertive cousin of other BRCW/Sulzer products—but tuned to the Southern's needs.

Design: a straightforward diesel-electric done properly

The Class 33 is diesel-electric in the classic British sense: a single diesel engine drives a generator, which feeds traction motors. What made it "right" for its era was not exotic technology, but sensible system choices and robust execution.

• Builder: Birmingham Railway Carriage and Wagon Company (BRCW)
• Prime mover: Sulzer 8LDA28
• Power: 1,550 bhp (engine)
• Wheel arrangement: Bo-Bo
• Maximum speed: 85 mph
• Train supply: Electric Train Heat (ETH)
• Braking: dual (air and vacuum)

Why they were called "Cromptons"

British traction nicknames are often half-joke, half-truth; "Crompton" is unusually literal. The nickname is generally linked to the Crompton Parkinson electrical equipment associated with the class. Whether you saw them in green with headcode blinds or later in blue on engineers' work, a Class 33 was simply "a Crompton".

Visually, the class also carried a Southern signature: two-digit headcode blinds between the cab windows, a reminder that these locomotives were meant to slot into a railway where reporting numbers mattered and passenger traffic was king.

Building the fleet: 98 locomotives, then a lifetime of reinvention

A total of 98 locomotives were built in the early 1960s, originally numbered D6500–D6597. In service, they settled into the Southern Region's diesel landscape quickly. They were the kind of locomotive that makes a region's diagrams easier: powerful enough to handle heavy summer trains, fast enough to keep out of the way on main lines, and general-purpose enough that you can throw them at parcels, engineers' trains, or reliefs without having to rewrite the rule book.

Their reputation was helped by the very thing that shaped their specification: avoiding the worst of steam-heat boiler trouble and leaning into ETH-centric operation where possible. The Southern didn't need them to be glamorous; it needed them to be there, day after day, and the class became associated with exactly that kind of dependable utility.

Subclasses and specialist variants: where the Class 33 gets properly interesting

The Class 33 is often talked about as if it's one uniform type, but its fame partly comes from the opposite: it developed some of the most characterful sub-groups of any "standard" BR diesel.

Class 33/0 — the standard locomotives

The bulk of the fleet became the Class 33/0: standard-width locomotives, ETH-fitted, Southern workhorses. If you picture a Class 33 on a parcels working, an engineers' train, or a summer relief heading west out of London, you're probably picturing a 33/0.

Class 33/2 — the narrow-bodied "Slim Jims"

Then there's the truly niche group: Class 33/2, the narrow-bodied locomotives built for the Hastings line, whose restrictive tunnels demanded a reduced width. This is the sort of engineering compromise that feels uniquely British: instead of rebuilding tunnels, build a small batch of locomotives that can fit them.

They gained the nickname "Slim Jims"—a rare case where the nickname is both obvious and accurate. Only a small number existed, but they loom large in enthusiast memory because they embody that "make it work with what you've got" approach that defined so much of everyday BR practice.

Class 33/1 — push-pull "Bagpipes" and the Bournemouth story

The most operationally famous variant is the Class 33/1, created for push-pull work. Instead of running round at termini, the locomotive could be controlled from the driving end of a fixed formation—most famously with 4TC trailer control sets on services associated with the Bournemouth line and onward running to non-electrified destinations.

The 33/1s picked up their own nickname: "Bagpipes"—one of those bits of railway folklore that became part of the class's identity, even for people who never cared why the name started.

This push-pull work is also where the Class 33 brushes up against one of the Southern's strangest historical operating features: street running at Weymouth. The Class 33 push-pull story sits in that wider world of Southern improvisation—do what you must to keep through services working smoothly.

What they actually did: the Southern Region's "everything diesel"

To understand the Class 33 properly, you have to think in diagrams, not categories. A Class 33 didn't live a single-purpose life; it lived a timetable life.

• Seasonal passenger trains: heavy summer holiday traffic demanded something more muscular than smaller Type 2s.
• Parcels and vans: time-sensitive, frequent, and often operating at passenger-like timings.
• Freight and engineers' work: especially where passenger heating demands were lower and the locomotives could be used hard.
• Inter-regional oddities: ports, resorts, London termini, and cross-country links produced a spread of duties that rewarded a locomotive with ETH and decent speed.

This is where the Class 33 earns its reputation. Many British diesels are famous for a headline: a record run, a flagship express, a signature freight flow. The Class 33 is famous for being the traction manager's friend—capable, predictable, and adaptable.

Decline, afterlife, and preservation: why you still see them

As newer traction arrived and electrification expanded, the Class 33 inevitably moved down the priority list. But unlike some classes that vanish quickly once displaced, 33s kept finding roles: departmental work, charter use, heritage lines, and occasional duties where their capabilities and route knowledge still made sense.

The class has a notably strong preservation footprint. The reason is simple: they're the right size for heritage operations (powerful but not absurdly heavy), mechanically comprehensible in a way later traction often isn't, and emotionally tied to a region whose railway identity people care about.

And on preserved lines, they often do the job they always did best: hauling varied trains without complaint, making the railway run to time, and sounding—especially under load—like the Southern Region's diesel era made audible.

Summary

The British Rail Class 33—the BRCW Type 3, the Crompton—was a class of 98 Bo-Bo diesel-electric locomotives built for the Southern Region, powered by a Sulzer 8LDA28 engine at 1,550 bhp and geared for 85 mph running.

It became iconic not through a single glamorous duty, but through relentless usefulness: passenger, parcels, freight, and engineers' work across a mixed electrified/non-electrified region. Its story is made richer by its variants—the push-pull 33/1 "Bagpipes", and the narrow-bodied 33/2 "Slim Jims"—each a very British answer to a very specific operational problem.

In other words: the Class 33 is not just a locomotive class. It's a portrait of how the Southern Region chose to modernise—practical, adaptable, and slightly idiosyncratic, in the way that makes British railway history feel alive.