Ford Sierra

They say that institutions aren't for messing with. Radio 4, fish and chips, and rainy bank holidays – and back in 1982, you could add the Ford Cortina to your list. The Cortina was the dad's car of choice – and because it was the motor for Everyman, it remained Britain's bestselling car throughout the 1970s. Everyone loved the Cortina: sales reps, bank managers, policemen – and the low-lives they were chasing.

But come the 1980s, we wanted sophistication – and the simple-to-goodness Cortina couldn't reinvent itself. However Ford had it all in hand – and in September 1982, went from boxy to organic in one fell swoop.

The Sierra story started five years earlier under the codename Toni. Ford's Vice President of Design, Uwe Bahnsen, wanted to oversee a forward-thinking project – one that would see Ford producing a cutting-edge design that harnessed the free energy-saving benefits of aerodynamics.

Results in the wind tunnel were fantastic – its drag coefficient (a term only engineers used before 1982) was 0.34, compared with the Cortina's brick outhouse of 0.45.

But under the skin, the mechanics were familiar. The engine and gearboxes were Cortina carry-overs – a sure sign that Ford didn't want to completely alienate its clientele. Shocking them with a 21st-century look was one thing; driving them into the arms of the opposition was something else.

When the Sierra made its appearance at the 1982 Birmingham Motor Show, it made the national news. Trevor McDonald and Angela Rippon solemnly proclaimed the end of the Cortina.

However, the striking hatchback wasn't only controversial for its styling. The kit-car maker, Dutton, slapped a lawsuit on Ford – because it had been marketing its own Sierra since 1980.

The new car couldn't come a moment too soon – Ford's dealers had stocks of unsold Cortinas piling up in their back-lots, and had been biting their nails waiting for the reactions of potential buyers. A Cortina replacement was long overdue, but they just weren't sure the Sierra was going to hit the spot with buyers.

Just like the Cortina, there was no reason for the Sierra not to succeed. The range was massive – from the poverty-spec 1.3-litre base model (with black nosecone and naked steel wheels), to the pretty, wood-lined, V6-powered 2.3-litre Ghia, the Sierra offered something for every rep in the team. But it wasn't enough.

Buyers weren't convinced, though, and the slippery new car soon picked up the "jelly mould" nickname, and it became clear that Ford would have a fight convincing a nation of dads that they needed a Sierra in their life. Dealers relied on Escort sales as Sierras languished on their frontages.

The combination of recurring stories about the car's crosswind instability, and poor value compared with the Vauxhall Cavalier did nothing to improve the situation as 1983 came and went.

Sporting Sierras were rolled out in succession to glam up the range – first there was the frankly strange V6-powered XR4i, followed by the capable four-wheel-drive XR4x4, and finally the marvellous 204bhp Sierra Cosworth.

However, it wasn't until the range received the handsome Sapphire saloon derivative in 1987 that the Ford Sierra really started rattling the Cavalier's cage. At last the Sierra had become the car that dads actually wanted – and sales were turned around.

Now the old-looking Cavalier was on the back foot, and Ford was heading for the number one position in the rep's hit parade.

Ford's great gamble had paid off – and although it had taken years for success to come, the Sierra proved to be one of the most influential cars of its decade. Today, as it currently occupies that murky netherworld awkwardly located between secondhand and classic, its true importance should never be under-estimated.

Would contemporary cars look quite as smooth as they do had it not been for the Sierra? It might have been a British institution, but replacing the Cortina with something so futuristic was a huge gamble.

Sadly, Ford didn't benefit. The Sierra cost the company so much in terms of terms of those early sales that it retreated to conservatism – and in doing so, they handed the initiative to their bitter rivals, Vauxhall. Dad, though, was happy.