Sebastian Vettel has opened up about his early years in Formula 1 in the new ARD documentary Being Sebastian Vettel – and how German manufacturer BMW initially supported him before ultimately letting him go.

The four-time F1 world champion said: "In the end, the whole BMW story didn't really work out as originally planned. […] I actually already had one foot in the door because my contract with BMW stated that I would get a seat in Formula 1. But that never really materialised."

At least not beyond his initial appearances: Vettel made his first F1 appearance during a Grand Prix weekend in Friday practice at the 2006 Turkish Grand Prix in Istanbul, immediately setting the fastest time.

In 2007, he also made his Grand Prix debut for BMW Sauber. With regular driver Robert Kubica sidelined by injury, reserve driver Vettel stepped in for the United States Grand Prix at Indianapolis – and scored his first world championship point straight away.

Why BMW doubted Vettel's abilities

But that was as far as it went: BMW let Vettel leave. Explaining the reasons in the new television documentary, Vettel said: "During my time at Sauber, there was this 'rumour' going around that Sebastian wasn't that fast and wasn't that good. And yes, I can understand how people might have got that impression. Maybe there was even some truth to it, in a way, because I needed a bit of time before everything clicked."

"Then the whole situation turned on its head because, on BMW's side, I wouldn't say there was less interest, but there just wasn't the same drive behind it."

What he lacked was a clear path forward: "Here's your seat. Next year we'll do this, the year after that we'll do that."

Sebastian Vettel, BMW Sauber F1.07

Photo by: Sutton Images

How Vettel got his Formula 1 opportunity with Toro Rosso

Vettel found exactly that opportunity within the Red Bull organisation: Just a few weeks after making his Formula 1 debut for BMW Sauber, he became a full-time driver for Toro Rosso.

Former Red Bull motorsport adviser Helmut Marko said in the new Vettel documentary: "Thank God the people at Sauber weren't convinced of Vettel's abilities, which meant we were able to get him. And then it became clear that here was someone who not only had the speed, but was also technically capable and prepared to put in the hard work."

According to Vettel, his move from BMW Sauber to Toro Rosso was ultimately decided at the very top of Red Bull: "In the end, Dietrich Mateschitz put his foot down and said: 'Let's not spend too much time discussing this. Give the kid a chance. If it works out, great. If it doesn't, it doesn't.'"

Vettel's 2008 Monza victory as a turning point

Just how well it worked out became clear a little over a year after Vettel joined Toro Rosso: He claimed a sensational victory at the 2008 Italian Grand Prix in Monza – the first F1 win for a team owned by the Red Bull group.

In the Vettel documentary, Lewis Hamilton said: "I think that was a really defining moment, showing that this guy's got what it takes to become world champion."

Marko added that "it was because of that success that we brought him to Red Bull for the following year".

There, Vettel also secured the team's first victory in Formula 1 history – before becoming world champion for the first time in 2010. By then, BMW had already withdrawn from Formula 1.

Vettel acknowledged that a "certain amount of luck" had also played a part in how his career unfolded.

"Having the right people around at the right moment, the right things happening, and so on. But you still have to deliver the right performance. And I think a lot of what we call luck is actually in your own hands."