It is 99 years since William Morris bought the old military college in Cowley and started making cars there, but in the roller-coaster ride from then to the high-tech, robot-driven factory which is today producing the runaway success story that is the Mini, there have been peaks and troughs of investment all the way.

Among the highest of the peaks was BMW’s £800m buy-out of the MG Rover Group from British Aerospace (BAe) in 1994 — followed by yet more money being pumped into the Cowley works, not least into a £100m new paint shop, much to the relief of local residents who were then being sprayed from time to time with flecks of paint from the old one.

And last week came another high with BMW’s £500m investment commitment over the next three years.

In the era that has followed the German company’s purchase of the British motor conglomerate, it is all too easy to forget just how dire the future of the Cowley plant (and therefore, some might say, the whole Oxfordshire economy) looked before the takeover.

In those days, for instance, as a Botley resident who worked at the plant in the 1990s told The Oxford Times, industrial relations were so bad that people would walk out over small things, like the flex of the kettle being slightly frayed at tea break.

“That was a health and safety issue,” he said. (Shades of the 1959 film I’m Alright Jack there, in which Peter Sellers played a motheaten old shop steward).

But it was industrial relations that were frayed in 1990 when BAe called for 1,600 redundancies out of a workforce of 8,500.

The following year the so-called New Deal with Honda came into force and BAe demanded more redundancies, bringing the Cowley headcount right down to 5,000 — a far cry from the heady days of the troubled 1970s when as many as 25,000 people worked at the factory — which then comprised the north and south works plus the Pressed Steel body works.

Not that the takeover by BMW solved simmering problems at the site at the drop of a hat. Far from it.

For years afterwards the German press dubbed the company’s loss-making British subsidiary “the English patient” and I remember visiting BMW’s Munich headquarters in 1997, to see how BMW’s German workers fared.

BMW was then floating a tantalising carrot in front of the noses of its Oxford employees, or associates as it likes to call them: provided they voted to adopt some revolutionary and foreign-seeming work practices (such as the working time account, still in operation now) the company would pump money into the Oxford plant to produce the Rover 75.

I recall being impressed (not least by the beer dispensing machines on the factory floor, which to my knowledge were never introduced here).

It seemed to me then that Cowley workers would be behaving like turkeys voting for Christmas if they failed to accept BMW’s offer.

And in the event — sigh of relief all round — accept it they did. But only to lurch into the next crisis two years later, in 2000.

This time around, BMW announced it wanted to break up MG Rover.

It sold Land Rover to Ford and the entire Longbridge plant to the ill-fated Phoenix group (for a purchase price of £10) — once again leaving Cowley workers in a slough of despond, wondering what would happen to them.

But a peak rather than a trough was around the corner for Oxfordshire’s biggest employer.

BMW transferred the entire Rover 75 production to the (ultimately) doomed Longbridge — and the bright day of the new Mini dawned for Cowley in 2001 when the first of the little cars rolled off the production line.

The rest, as they say, is history.

But last week’s announcement that BMW is to further consolidate its position in Oxford with that £500m capital injection underlines the Mini success story — and washes away the slightly bad taste left in the mouth by the dismissal in February 2009 of 850 agency workers at the start of the present economic downturn.

Prime Minister and Witney MP David Cameron said: “It’s a tremendous vote of confidence in the skills and capabilities of the company’s British workforce and in the future of British manufacturing.”

Certainly it sends out a signal that BMW at least has confidence in the future of the UK economy and thinks the recession has been less bad than was expected in 2009.

Ironically, as it happens, many of Cowley’s greatest peaks have occurred in times of recession.

Its major growth happened in the 1930s Great Depression when the Morris works, under the leadership of William Morris, later Lord Nuffield, actually advertised for workers — who then arrived in Oxford, often having walked for miles, sleeping in hedgerows, to take up the jobs.

And even in the 1950s men skilled in declining trades found jobs with the car builders. For instance a blacksmith in Burford cycled every day into Oxford to work at Morris Motors’ Oxford Radiators, then in Woodstock Road; the irony being of course that he himself could not afford one of the cars he helped to build.

The 1990s recession occurred amid fears that the whole Cowley car building business could close at any minute.

After all it had only been artificially resuscitated in 1975 when the Labour government bought a majority shareholding.

But in the end, following the New Deal (which hoisted the ratio of 11 cars per worker per year to 30.6 cars), it led to BMW’s takeover.

In those days, brain had not yet replaced brawn at the south and north works — where the Oxford Business Park now stands.

The present BMW plant stands on the old Pressed Steel plant, which was an integral part of the car building enterprise.

It’s all a far cry from William Morris’s initial push to introduce American type production lines, similar to Henry Ford’s, into Britain.

Now German methods are here instead and, some might say, the future looks as bright for car building in Oxford as it has ever done in the past. But without doubt it has been a bumpy ride.