World Championships 2017: Usain Bolt & Mo Farah headline London event

Farah is returning to the stadium where he won double Olympic gold at the 2012 Olympics

Jamaican sprint great Usain Bolt and British distance legend Mo Farah will attempt to sign off with gold at the World Championships which begins in London on Friday.

The pair, who have 28 world and Olympic titles between them, will both retire from the track by the end of the season.

Elsewhere, Jamaica's Elaine Thompson and Dutchwoman Dafne Schippers renew their sprint rivalry, while Britain's Laura Muir will attempt a formidable 1500m-5,000m double.

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With Bolt not defending his 200m title, 400m world record holder Wayde van Niekerk will attempt to double up and establish himself as one of the new figureheads for the sport.

Fellow South African Caster Semenya is also fighting on two fronts, stepping up to 1500m as well as attempting to regain the 800m title she won in 2009 and 2011.

The Championships begin on Friday, five years to the day since Great Britain won three Olympic gold medals in less than an hour on 'Super Saturday' at the same venue.

Bolt draws curtain on career

Bolt's 100m world record of 9.58 seconds came in the 2009 World Championships

Bolt originally intended to retire in the wake of Rio 2016. However he reconsidered that plan after his sponsor suggested a London farewell a year later instead.

Now 30, the Jamaican had a slow start to the season, dipping under 10 seconds for the first time in Monaco a fortnight ago.

He is only the joint-seventh fastest man over 100m in 2017, but has a history of rising to the big occasion.

Only once in seven major 100m finals has Bolt failed to win gold, and that was after a false start at the World Championships in Daegu in 2011 took him out of the race.

Coleman, one of Bolt's foremost rivals, is still a student at University of Tennessee

Twenty-one-year-old American Christian Coleman - who ran a world-leading 9.82 in June - a 35-year-old Justin Gatlin and 2011 world champion Yohan Blake may be Bolt's biggest rivals for gold in the final on Saturday. Bolt's final race before retirement is likely to be the 4x100m relay final seven days later.

A homecoming farewell for Farah

Will we see the Mobot once again at London Stadium?

Farah's 5,000m and 10,000m double was one of the defining memories of the London Olympics five years ago.

Since then the 34-year-old has repeated the feat at World Championships in Moscow and Beijing as well as last summer's Rio Olympics, and is favourite to do so once again before shifting his focus to marathon.

However he is facing a crop of young pretenders with Ethiopian teenager Abadi Hadis the fastest this year over 10,000m and 23-year-old compatriot Muktar Edris leading the 5,000m time charts.

Farah's preparations have been at times sidetracked by questions over training methods however.

Computer hackers released documents in July that showed Farah's blood tests initially raised suspicion before later being cleared. His coach Alberto Salazar is under investigation by the US Anti-Doping Agency, while UK Athletics staff may have failed to properly record infusions of a controversial supplement given to Farah.

Both Farah, who has refused to speak to newspaper journalists going into the championships, and Salazar have denied any wrongdoing.

Farah's 10,000m final headlines Friday's opening day of competition with Wednesday's 5,000m heats deciding the line-up for the final on Saturday, 12 August.

Home hopes

Muir, 24, combines her athletics career with studying to become a vet

Beyond Farah, Britain has more medal hopes than expectations.

Muir broke Dame Kelly Holmes' 1500m record at London Stadium last year, but found the pace of Kenya's Faith Kipyegon and Ethiopia's Genzebe Dibaba too hot to handle over the final 800m in a tactical Olympic final in Rio.

Kipyegon and Dibaba are both in the field in London along with the Netherlands' Sifan Hassan, who has the three fastest times of the year, and Semenya.

British Athletics performance director Neil Black gave Muir only "a 1%" chance of adding the 5,000m to her schedule after she suffered a foot injury in June, but Muir is determined to pursue the longer distance after breaking the British indoor record in January.

Katarina Johnson-Thompson will attempt to fill the void left by Jessica Ennis-Hill's retirement in the heptathlon, taking on Olympic champion Nafissatou Thiam.

Tom Bosworth broke the racewalking mile record in July and will aim to improve on his sixth-place finish in the 20km in Rio.

Johnson-Thompson scored a career-best of 6,691 in the heptathlon at Gotzis in June

Colin Jackson and Tony Jarrett are the only Britons to have gone faster over the 110m hurdles than the 13.14 seconds that Andrew Pozzi clocked in July and the 25-year-old Holly Bradshaw has broken the outdoor British record twice already this season in the pole vault. Robbie Grabarz and Sophie Hitchon are Olympic medallists and possible contenders in the high jump and hammer respectively.

But overall, and given the absence of the injured Greg Rutherford, UK Sport's target of at least six medals looks like being a tall order.

"Without a doubt it's doable," said Black. "If we deal with home advantage well and get a little bit of luck, then I think we meet the medal target."

How can I be there?

London won the right to host the World Championships ahead of Doha in November 2011

With one week to go, more than 660,000 tickets had already been sold for the 10 days of the championships.

A small number of new tickets for all sessions were made available on Tuesday.

While those for the men's 100m final and the 5,000m and 10,000m finals likely to feature Farah appear to have already sold out, there is still the chance to see stars such as Van Niekerk and Muir compete for medals.

The prospect of a packed stadium for the best athletes in the world is the realisation of part of London 2012 chairman Lord Coe's promise for the Games' legacy. He insisted that track and field had to be central to the venue's future. rather than it be used exclusively for football.

BBC coverage

Ennis-Hill (left) will also be awarded the gold medal from the 2011 championships in a special ceremony in the 6 August evening session after Tatyana Chernova (centre) was stripped of the title for doping

BBC One and BBC Two will show all the best of the action live from London Stadium with a punditry team that includes Olympic legend Michael Johnson and, for the first time, London 2012 gold medallist Ennis-Hill.

A daily highlights programme on BBC Two will bring together the choice moments and all the talking points.

There will also be full coverage on BBC Radio 5 live led by correspondent Mike Costello and Olympic gold medallist Darren Campbell.

You can access both radio and television coverage right here on the BBC Sport website and app, alongside text commentary featuring rolling highlights and analysis.

And there will be exclusive insight behind the scenes of the championships via BBC Sport's social media accounts on Facebook, Instagram and Twitter.

Watch Michael Johnson's top five moments

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