Ten to watch at the London Games

The world's greatest athletes descend on London in July for the 2012 Olympics. Martyn Herman highlights 10 to watch when the Games get underway: 

Usain Bolt (athletics): The face of the Beijing Olympics where the Jamaican sprinter's jaw-dropping speed earned him three golds in the 100m, 200m and 4x100m relay and three world records.

He has been pretty much unbeatable when it matters since, winning the five golds from the last two world championships -- his only blemish coming in Daegu where he was disqualified after false-starting in the 100m.

Tickets to watch Bolt race in London will be like gold dust, but those with seats better not be late as some predict, if he is firing on all cylinders, he can lower his 100m world record mark below 9.5 seconds.

Yelena Isinbayeva (athletics) 

The Russian manages to combine grace and power in the pole vault to devastating effect, soaring higher and higher since setting her first world record of 4.82 metres in Gateshead in 2003.

Since then she has steadily raised the bar to 5.06 metres, considerably higher than one of London's famous red double decker buses, claiming five world titles and the Olympic golds in Athens and Beijing.

Should the pole vault queen win in London, when she will have turned 30, she will become the first female track and field athlete to win gold at three consecutive Games.

David Rudisha (athletics)

The latest in a long line of Kenyan two-lap specialists, the 23-year-old world record holder will be aiming for his first Olympic gold when he lines up in the 800 metres in London.

Rudisha, a Maasai tribe warrior, set a world record of 1:41.09 in Berlin in 2010 and then a few weeks later lowered it again to 1:41.01. He is the current world champion and was voted world athlete of the year for 2011.

London Olympic chairman Sebastian Coe will have a keen eye on the lanky Rudisha's performance, having once held the world record over the distance himself. Rudisha said watching videos of Coe inspired him to run.

Nataliya Dobrynska (athletics)

All eyes will be on the mourning Ukrainian multi-eventer's every move as she takes on British darling Jessica Ennis in the heptathlon.

She emerged from nowhere to win the gold in 2008 and again upset the form book at the recent world indoor championships, beating Ennis and Russian world champion Tatyana Chernova to gold in a new pentathlon world record.

Dobrynska suffered heartbreak recently when her husband and coach Dmytro Polyakov died after a lengthy battle with cancer.

Allyson Felix (athletics)

The shining star of the U.S. women's track and field team, she is still without an individual gold at an Olympics, having to make do with silver in the 200m at Athens and Beijing.

The wholesome daughter of a Christian minister in southern California, Felix was denied a fourth successive world championship 200 gold in Daegu last year.

Expect to see a lot of her in London if she doubles up in the 400m and competes in both relays.

Kenenisa Bekele (athletics)

Almost lost in the hype surrounding Bolt in Beijing, the Ethiopian's golden double in the 5,000m and 10,000m was arguably an even greater achievement.

The world record holder at both 5,000 and 10,000, he can justifiably lay claim to being one of the greatest distance runners of all time and will be the man to beat in London if he can arrive fully fit after two years of injury problems.

After pulling up in the 10,000m at the 2011 world championships with a ruptured muscle, his aura of invincibility was under threat and he must decide whether his body can cope with the Olympic double again.

Michael Phelps (swimming)

Quite simply, American Michael Phelps owned Beijing's water cube in 2008, his size 14 feet and huge arm span powering him to eight gold medals and sparking endless online chatroom debates about whether he or Usain Bolt deserved to be called the greatest sportsman on earth.

That feat gave him the record for the most gold medals at a single Olympics, beating the seven of Mark Spitz in Munich, and few would bet against him raising his overall haul of 16 Olympic medals in London which he says will be his last Games.

Even a relatively modest haul of two medals of any colour would tie him with the 18 Olympic medals of former Soviet gymnast Larisa Latynina.

Katie Taylor (boxing)

Women's boxing makes its Olympic debut in London and Ireland's Katie Taylor will get the chance to add to her already groaning trophy cabinet in the ExCel Centre.

A three-times world and five-times European champion already, she has also represented Ireland in soccer and is rightly regarded as one of the Emerald Isle's greatest sportswmomen.

A devout Christian, she has become something of a celebrity, meeting U.S. president Barack Obama at the White House, starring in a rap video with Tinie Tempah and was last year's Grand Marshal at Dublin's St Patrick's Day parade.

Federica Pellegrini (swimmer)

Born near the watery city of Venice she learnt to paddle before she could walk, so it is appropriate that the glamorous Pellegrini has made her name as the her country's most successful female swimmer.

Won the 200m freestyle in Beijing to become the first Italian woman to win an Olympics swimming gold and currently holds the world record in the 200 and 400 freestyle.

At the Rome world championships she became the first woman to go under four minutes in the 400m.

A magnet for camera lenses, she regularly appears on countless glossy magazine covers.

Mark Cavendish (cycling)

The Isle of Man cyclist could get the ball rolling on Britain's gold medal haul by winning the men's road race.

He has other things on his mind first, though, as he concentrates on the Tour de France in which he already owns 20 stage wins.

He became the first British cyclist to win the sprinter's green jersey outright on the Tour last year but gold will be the colour he craves once the Olympic torch is lit.