Lewis Hamilton has described Valtteri Bottas as the best team-mate of his career following news the Mercedes driver will be heading to Alfa Romeo.

Bottas, 32, has won nine races and helped Mercedes to four constructors' championships since joining the team back in 2017.

The Finn is now due to take the place of the retiring Kimi Raikkonen at Alfa Romeo, with George Russell expected to line up as Hamilton's new team-mate with the Silver Arrows in 2022.

Bottas will bring plenty of experience to Alfa Romeo, having twice finished as runner-up to Hamilton in the drivers' standings and also secured 54 podiums in 92 starts for Mercedes.

Reigning champion Hamilton says Bottas is a greater driver than he realises and has savoured sharing a garage over the past five seasons.

"I'm immensely proud to have worked alongside Valtteri for the last five years," he wrote on social media.

"Together, we've been part of a team that has delivered four constructors' championships, and we've motivated one another to keep pushing through the ups and the downs.

"He has been the best team-mate I've had the pleasure of working with. Your speed and resilience has been impressive but where you truly stand out to me is the human being you are and gentleman.

"You are greater than you know and I know there's a bright future ahead for you.

"Thank you Valtteri for all your support and amazing contributions to this team. You will be missed. I wish you all the best for your future endeavours. Let's finish off strong and get that 8th for the team."

Alfa Romeo have announced Valtteri Bottas will leave Mercedes to replace the retiring Kimi Raikkonen on a multi-year deal from next season.

Bottas has raced for Mercedes since 2017, winning nine races across that period and helping the Silver Arrows to four constructors' championships.

However, the 32-year-old's future has been the subject of much speculation in recent months and it has now been confirmed he will leave Mercedes at the end of the 2021 season.

The Finn's exit paves the way for George Russell's likely graduation to Mercedes to partner fellow Briton Lewis Hamilton from next season onwards.

Bottas will bring plenty of experience to Alfa Romeo, having twice finished as runner-up to Hamilton in the Driver Standings and also secured 53 podiums in 92 starts for Mercedes. 

"A new chapter in my racing career is opening," he said in a statement on Monday. 

"I'm excited to join Alfa Romeo Racing ORLEN for 2022 and beyond for what is going to be a new challenge with an iconic manufacturer.

"Alfa Romeo is a brand that needs no introduction; they have written some great pages of Formula 1 history and it's going to be an honour to represent this marque. 

"The potential of the setup in Hinwil is clear and I am relishing the opportunity to help lead the team forward up the grid, especially with the new regulations in 2022 giving the team a chance to make a leap in performance.

"I'm grateful for the trust the team has put in me and I cannot wait to repay their faith: I'm as hungry as ever to race for results and, when the time comes, for wins. 

"I know Fred [Vasseur] well and I am looking forward to getting to know the rest of the team I am going to work with, building relationships as strong as the ones I have at Mercedes.

"I am proud of what I have achieved in Brackley and I am fully focused on finishing the job as we fight for another world championship, but I am also looking forward to the new challenges that await me next year."

The news of Bottas' arrival comes after Raikkonen announced last week he is to retire at the end of the season. Alfa Romeo have yet to announce who will partner Bottas next year.

Bottas will reunite with Alfa Romeo team principal Vasseur after the pair previously worked together at ART in F3 in 2009 and 2010, and in GP3 in 2011.

Vasseur said: "It is a pleasure to welcome Valtteri to the team and we are looking forward to our journey together. With him, we bring to Hinwil a strong team player with experience at the sharp end of the grid.

"Valtteri has been an integral part of a team that rewrote the history books and he has four constructors’ world titles to his name: he is the right driver to help Alfa Romeo Racing ORLEN make a step forward towards the front of the grid."

Kimi Raikkonen will not take part in the Dutch Grand Prix after testing positive for coronavirus. 

Raikkonen confirmed on Wednesday that he will retire from Formula One at the end of the 2021 season. 

Heading into the weekend there were just 10 races - including Sunday's trip around the Circuit Zandvoort - left in Raikkonen's F1 career, though he is now having to skip the event, which has been reintroduced to the calendar this year. 

The 41-year-old Alfa Romeo driver is isolating in his hotel, with the team confirming he is not showing any symptoms and is in good spirits. 

Robert Kubica, who has not raced in F1 since Abu Dhabi in 2019, will stand in for the 2007 world champion. 

"Robert has been reserve driver of Alfa Romeo Racing since the start of the 2020 season and has driven the team’s C41 in three practice sessions this year," Alfa Romeo said via Twitter. 

"With 97 Formula One starts to his name and experience with 2021 Formula One machinery, he will be ready for action and to give his best for the team." 

Raikkonen will require a negative test result in order to return to the paddock, so his status for the Italian Grand Prix remains uncertain for now. 

A joint FIA and F1 statement read: "The FIA, Formula 1 and Alfa Romeo Racing can today confirm that during onsite PCR testing for the 2021 FIA Formula 1 Dutch Grand Prix, Kimi Raikkonen has tested positive for COVID-19. 

"In accordance with COVID-19 protocols he will take no further part in this Event. All contacts have been declared. The procedures set out by the FIA and Formula 1 will ensure no wider impact on the Dutch Grand Prix." 

Christian Horner has revealed that Williams and Alfa Romeo have expressed an interest in signing Alex Albon for the 2022 Formula One season.

Albon lost his Red Bull seat to Sergio Perez at the end of last season and was relegated to the role of reserve driver.

With Kimi Raikkonen retiring and George Russell strongly fancied to replace Valtteri Bottas at Mercedes, Albon could be back on the grid next year.

Red Bull boss Horner hopes Albon gets another chance and will help the 25-year-old kickstart his career.

Horner said: "I think Alex, he deserves a seat in Formula One next year and I think there's quite a bit of interest in him for next year and we'll do whatever we can to try and enable that.

"I hope that nothing prevents him from realising one of those opportunities. He's a talented driver; it's subject to George moving. Kimi's retiring – that does open up opportunities – so I am sure it will get resolved over the next week or so.

"We're looking at external teams. Williams and Alfa have both expressed interest and yes, we're keen to see him back racing in Formula One, and hopefully that can get resolved over the next few days."

Horner added: "We’ll be supportive of [Albon] racing elsewhere. I hope that Mercedes don't prevent that from happening. He deserves that chance. So, we're doing our best to help him and we’ll see what happens."

Mercedes team principal Toto Wolff insisted he would not stand in Albon's way of a place on the grid despite their backing of Nyck de Vries, the 2019 Formula Two champion who is vying to make the step up.

"I would never block someone like Alex Albon," said Wolff. "He's a fantastic guy, personality is great, I was personally sad to see him going [in 2020], and if he has a chance in a Formula One car I think that's the right thing to do.

"But equally, maybe Nyck has. So we'll have to look at the open spaces at Alfa and at Williams and try to find a solution."

Kimi Raikkonen says he "wouldn't change a single thing" about his Formula One career and does not expect to miss racing once he retires at the end of the season. 

The 2007 world champion announced on Wednesday that this will be his final campaign. 

Finn Raikkonen made his debut at the 2001 Australian Grand Prix and has gone on to start a record 341 races, winning 21 and finishing on the podium 103 times. 

The 41-year-old Alfa Romeo driver insists he will walk away with no regrets. 

Asked what his biggest strength as a driver is, he said: "I don't know if I have one! I had a good run, I'm happy with what I achieved. 

"Obviously you want to win and it's not easy to win. I wanted to win a championship, I got close quite a few times and managed to win it with Ferrari, so happy that it happened, especially with them. 

"But the rest, strength or not strength, I don't care. I had fun and I did it my way, and I wouldn't change a single thing even if I could, because otherwise then maybe we wouldn't be sitting here today if you changed one thing along the way. No complaints – I cannot really complain." 

Raikkonen has not thought about what comes next – and is certainly in no rush to commit to anything other than his family. 

He said: "No plans. I don't want to have some schedule put on, because obviously the last 18, 19 years in F1, since I started, I did rally in those two years [away from F1 in 2010 and 2011], there was always a schedule, always what is coming next and what is this date and that date. So I don't want that. 

"That's for sure one of the big reasons why I want to also do something else. Obviously, there's other schedules: family, the kids' schools and kindergartens and that stuff. 

"But I don't want the family life to be dictated by when is the next race or test or flight or next work. I'm not in a rush, and I've not even thought about it at all. 

"Obviously I've known this situation for quite a while, so there's always obviously opportunities to do this or do that, but right now I'm not interested to even think about it." 

He added: "Will I miss the racing? I don't know. I've done it so long that I doubt that I'll start to miss it that much." 

Kimi Raikkonen has announced his impending retirement from Formula One.

The 41-year-old, who won the world title with Ferrari in 2007, will call time on his career at the end of the 2021 season.

Raikkonen made his F1 debut with Sauber at the 2001 Australian Grand Prix and spent five seasons with McLaren before a three-year stint with Ferrari.

He took a break from F1 but returned with Lotus in 2012, going on to join Ferrari again before moving to Alfa Romeo in 2019.

The Finn, who has 21 race wins and 103 podium finishes to his name, confirmed his decision in an Instagram post on Wednesday.

"This is it. This will be my last season in Formula 1," the post read.

"This is a decision I did during last winter. It was not an easy decision but after this season it is time for new things. Even though the season is still on, I want to thank my family, all my teams, everyone involved in my racing career and especially all of you great fans that have been rooting for me all this time.

"Formula 1 might come to an end for me but there is a lot more in life that I want to experience and enjoy. See you around after all of this! Sincerely Kimi."

Speculation mounted earlier on Wednesday that Alfa Romeo were considering making a move for Valtteri Bottas, whose is waiting to discover if he will remain Lewis Hamilton's team-mate next year.

Mercedes future is in doubt, with George Russell a potential replacement as Lewis Hamilton's team-mate for next season.