The BRM P83 marked the start of an unfortunate decline for BRM, and a fallow period in terms of wins which was to last four years.
After winning the World Championship in 1962, and finishing second for the next three years, there would be very little for the BRM team, or its fans to celebrate until a smattering of results in the early 1970s.
The BRM team had started out disastrously in the late 1940s, but had been on a continuous path of growth for roughly a decade. Twelve of the team's seventeen Formula One Championship race victories were gained in the period from 1962 to 1966, but that purple patch was about to end.
As was often the case in BRM history, a change in engine regulations proved problematic.
In 1966, the regulations would stipulate a maximum engine capacity of 3 litres normally aspirated, or 1½ litres supercharged.
BRM hedged their bets by developing two different engines, an H16, and a V12 in co-operation with Harry Weslake.
Alfred Owen eventually chose the complicated H16 engine, designated the P75, and the V12 design was sold to Weslake and went on to power the Eagle T1G.
Unfortunately the P75 was plagued with problems, so although the new engine and the new chassis, the P83, were ready for the 1966 season, they were not deemed raceworthy, and sat most of the season out.
They were finally introduced for the final three races of the season, but this only resulted in three retirements each for Hill and Stewart. BRM had suffered a disappointing season with Stewart's victory in the old P261 at Monaco being the highlight.
1967 BRM P83
Hill left BRM at the end of the 1966 season, which proved to be a wise move.
BRM doggedly persisted with the car which had been so unsuccesful the previous year,the P83, and its ridiculously unreliable engine. But poor performances were only outnumbered by non finishes. The engine was so unreliable that the engine, transmission and related problems caused 27 of the powerplant's 30 retirements from 40 entries.
A second place finish for Jackie Stewart in Belgium was the team's best result of the year. BRM dropped to a lowly sixth place in the International Cup for F1 Manufacturers. It was the lowest place the team had managed since the constructor's championship had been introduced in 1958.
For the second time in the history of British Racing Motors, an over complicated, 16 cylinder engine had proved to be the team's nemesis.
Jackie Stewart left the team, which also proved to be a wise move.
Graham Hill went on to win the Championship in 1968 with Lotus, and Jackie Stewart won in 1969 with Matra, whilst BRM floundered.
In 1968, BRM are listed as using no fewer than four different car designs, which probably tells its own story.
The first was the P115, which was introduced the previous year, and still carried the disastrous P75, 16 cylinder engine. It was supposedly over 100kg heavier than other cars, mainly thanks to the engine. The car managed just one race in 1968, and you might not be surprised to hear that it did not finish.
The second car was the P126 which was contracted out to Len Terry to design, and thankfully BRM introduced a new V12 engine, and finally got rid of the notoriously unreliable H16.
The P133 was the works built version of the P126, which had been built by Len Terry's company.
And finally there was the P138, another Terry design which only made a couple of races in the 1968 season.
It may sound like chaos, but at least BRM were now finishing, and they managed to finish fifth in the Constructors' Championship which was an improvement.
Pedro Rodríguez had scored most of the points to put the team in that position, but his reward was to be shunted off to the semi works Reg Parnell team.
1968 BRM P126
In 1969, BRM were joined by John Surtees, which was probably the reason for the decision to demote Rodríguez. But even having another World Champion driver on their team didn't improve their fortunes.
The team continued to use the the P133, and P138, and a new variant the P139 was introduced.
Although BRM managed to finish fifth in the International Cup for F1 Manufacturers, their points haul of just seven was a miserable total.
John Surtees left the team and long standing team boss Tony Rudd was asked to resign.