By 1978, Ford Europe was working on a new mid-range model to replace the Cortina/Taunus during the early 1980s, working under the codename "Project Toni".

Ford had confirmed during 1981, a year before the Sierra's official launch, that its new mid-range car would carry the Sierra name, signalling the end of the Cortina nameplate after 20 years and five generations.
In September that year, it had unveiled the Probe III concept car at the Frankfurt Motor Show, hinting at what the new car would look like when the final product was unveiled 12 months later.

At first, many found the design blob-like and difficult to accept after being used to the sharp-edged, straight-line styling of the Cortina, and it was nicknamed "the jellymould".
The shape served a purpose though, producing a drag coefficient of 0.34, a significant improvement over the boxy outgoing Cortina's 0.45.
The interior was more conventional, although Ford took a page from BMW by angling the center of the dashboard towards the driver.

Sales were slow in the first months - the situation being exacerbated by heavy discounting by Ford dealers of surplus Cortina stock from the autumn of 1982 onwards, with more than 11,000 new Cortinas being registered in 1983.
However in 1983, its first full year of sales, the Sierra managed nearly 160,000 sales in Britain, outsold only by the smaller Escort.
Ford had also launched the more conservatively designed Escort-based Orion saloon that year, which found favour with buyers who would otherwise have been the Sierra's target customers.

In West Germany, it was proving very popular from an early stage; within months of its launch, it was reportedly achieving treble the number of sales that the Taunus had been attaining - though in West Germany, the Taunus had not been quite as popular or iconic as its Cortina equivalent had been in Britain.

It was later in the Sierra's life that the styling began to pay off; ten years after its introduction, the Sierra's styling was not nearly as outdated as its contemporaries, even though all major competitors were newer designs, though the Sierra had been tweaked on several occasions and many new engines had been added.
The most notable changes came at the autumn of 1987, with a major facelift and the addition of a 4-door saloon (UK: Sapphire).
As other manufacturers adopted similar aerodynamic styling, the Sierra looked more normal.
At its peak, it was Britain's second best selling car in 1983, 1988 and 1989, and was still Britain's fifth best selling car in 1992.
Its best year was 1989, when more than 175,000 were sold.
However, it was outsold by the Vauxhall Cavalier in MK2 form during 1984 and 1985, and then from 1990 until its demise by the MK3 Cavalier.
Nevertheless, it comfortably outsold its second key rival, the Austin Montego, which was launched in April 1984.
Between 1985 and 1988, the Sierra faced fresh competition in Europe from the likes of the Renault 21 and Peugeot 405, while Japanese carmaker Nissan was producing its Bluebird model in Britain from 1986.

Early versions suffered from crosswind stability problems, which were addressed in 1985 with the addition of "strakes" (small spoilers) on the rear edge of the rubber seals of the rear-most side windows.
These shortcomings saw a lot of press attention, and contributed to early slow sales, when it was outsold by its key rival the Vauxhall Cavalier in 1984 and 1985.
Other rumours that the car hid major crash damage (in part true, as the new bumper design sprung back after minor impact and couldn't be "read" to interpret major damage) also harmed the car's reputation.
This reached near-hysterical heights in its early months on sale, with UK press making a report that Ford would reintroduce the previous Cortina model out of desperation.
These reports were swiftly denied by Ford.
However, sales began to rise during 1983, and it finished as Britain's second best selling car behind the Escort.
After being outsold by the Cavalier for the next two years, it regained its lead of the market sector in Britain during 1986, and a refreshed ra
By 1978, Ford Europe was working on a new mid-range model to replace the Cortina/Taunus during the early 1980s, working under the codename "Project Toni". 
Ford had confirmed during 1981, a year before the Sierra's official launch, that its new mid-range car would carry the Sierra name, signalling the end of the Cortina nameplate after 20 years and five generations. In September that year, it had unveiled the Probe III concept car at the Frankfurt Motor Show, hinting at what the new car would look like when the final product was unveiled 12 months later.
At first, many found the design blob-like and difficult to accept after being used to the sharp-edged, straight-line styling of the Cortina, and it was nicknamed "the jellymould". The shape served a purpose though, producing a drag coefficient of 0.34, a significant improvement over the boxy outgoing Cortina's 0.45. The interior was more conventional, although Ford took a page from BMW by angling the center of the dashboard towards the driver.
Sales were slow in the first months - the situation being exacerbated by heavy discounting by Ford dealers of surplus Cortina stock from the autumn of 1982 onwards, with more than 11,000 new Cortinas being registered in 1983. However in 1983, its first full year of sales, the Sierra managed nearly 160,000 sales in Britain, outsold only by the smaller Escort. Ford had also launched the more conservatively designed Escort-based Orion saloon that year, which found favour with buyers who would otherwise have been the Sierra's target customers.
In West Germany, it was proving very popular from an early stage; within months of its launch, it was reportedly achieving treble the number of sales that the Taunus had been attaining - though in West Germany, the Taunus had not been quite as popular or iconic as its Cortina equivalent had been in Britain.
It was later in the Sierra's life that the styling began to pay off; ten years after its introduction, the Sierra's styling was not nearly as outdated as its contemporaries, even though all major competitors were newer designs, though the Sierra had been tweaked on several occasions and many new engines had been added. The most notable changes came at the autumn of 1987, with a major facelift and the addition of a 4-door saloon (UK: Sapphire). As other manufacturers adopted similar aerodynamic styling, the Sierra looked more normal. At its peak, it was Britain's second best selling car in 1983, 1988 and 1989, and was still Britain's fifth best selling car in 1992. Its best year was 1989, when more than 175,000 were sold. However, it was outsold by the Vauxhall Cavalier in MK2 form during 1984 and 1985, and then from 1990 until its demise by the MK3 Cavalier. Nevertheless, it comfortably outsold its second key rival, the Austin Montego, which was launched in April 1984. Between 1985 and 1988, the Sierra faced fresh competition in Europe from the likes of the Renault 21 and Peugeot 405, while Japanese carmaker Nissan was producing its Bluebird model in Britain from 1986.
Early versions suffered from crosswind stability problems, which were addressed in 1985 with the addition of "strakes" (small spoilers) on the rear edge of the rubber seals of the rear-most side windows. These shortcomings saw a lot of press attention, and contributed to early slow sales, when it was outsold by its key rival the Vauxhall Cavalier in 1984 and 1985. Other rumours that the car hid major crash damage (in part true, as the new bumper design sprung back after minor impact and couldn't be "read" to interpret major damage) also harmed the car's reputation. This reached near-hysterical heights in its early months on sale, with UK press making a report that Ford would reintroduce the previous Cortina model out of desperation. These reports were swiftly denied by Ford. However, sales began to rise during 1983, and it finished as Britain's second best selling car behind the Escort. After being outsold by the Cavalier for the next two years, it regained its lead of the market sector in Britain during 1986, and a refreshed ra
Ford Sierra