Media playback is unsupported on your device Media caption Paralympians watch performers at the Olympic Park

Final preparations have begun for the London Paralympics opening ceremony, heralding 11 days of competition for athletes with disabilities.

Some 3,000 volunteers will take part in the event, which organisers have entitled Enlightenment.

Professor Stephen Hawking and actor Sir Ian McKellen will narrate the show, which is due to begin at 20:30 BST.

But there are doubts the Paralympic flame will arrive on time, as the torch relay is running an hour late.

Meanwhile, Malawi have withdrawn from the games due to lack of funding.

A Locog spokeswoman said they were still hopeful the torch being used in the relay would make it to the Olympic Stadium in time for the opening ceremony.

A back-up flame was earlier created at City Hall, to make certain the ceremony could start as planned.

The flame began its journey in Stoke Mandeville, the spiritual home of the Paralympic Games, on Tuesday night.

It will be carried by 580 torchbearers in total, and after being carried past some of London's most famous landmarks, will be used to light a scaled-down version of the Olympic cauldron.

UK Sport and the British Paralympic Association have set a minimum target of 103 medals this time from at least 12 sports, including swimming, athletics and rowing.

Human possibility

The opening ceremony - which will be broadcast on Channel 4 and BBC Radio 5 live - will signal the start of 11 days of competition by more than 4,000 athletes from 165 countries, including more than 300 athletes from ParalympicsGB.

Analysis Backstage, organisers and volunteers are busily applying final touches to props and paraphernalia - a wipe-down of a flag pole here, a lick of paint to a prop there. The ceremony explores the twin themes of reason and rights, and we're promised a journey of discovery, led by celebrated scientist Professor Stephen Hawking and Shakespeare's character Miranda from The Tempest. The cast includes 73 deaf and disabled professional performers and also well-known names like Sir Ian McKellen as a Prospero-type character, singer Beverley Knight and 3,250 volunteers aged 10-80 from all over the world. Organisers say the show is about challenging perceptions. There will be athletes, flags, royals and Tom Heatherwick's cauldron as expected. There will also be a Hadron collider and a fly-by by Aerobility - a charity that trains disabled people to become pilots - and the humble apple is also playing a key role in proceedings. "You all need to make sure you have an apple," said artistic director Jenny Sealey ahead of the ceremony. "Because everybody, 62,000 people in the audience will also have their apple. "We're asking people on television to make sure they have their apple. We want to stage the biggest ever apple bite." Paralympic organisers are looking to break records before the Games have even begun!

A capacity crowd of 80,000 people will watch the ceremony in Stratford, east London, which will be opened by the Queen and watched by the Duke and Duchess of Cambridge.

The start of the show will feature a flypast by Aerobility, a British charity that trains disabled people to become pilots.

Fifty specialist performers in the ceremony have taken part in an eight-week circus skills training programme in east London, and will take part in a high-wire act.

The show's two artistic directors have said the main themes of the ceremony will be empowerment and the challenging of perceptions of human possibility.

Prof Hawking - a world-renowned physicist who has motor neurone disease - will join Sir Ian McKellen to narrate a scientific "journey of discovery", inspired in part by Prof Hawking's own book A Brief History of Time.

The organisers have revealed that Prof Hawking will act as a guide to Miranda, a character from William Shakespeare's play The Tempest, through the show.

Sir Ian will play Prospero, another character from the play.

Co-artistic director Jenny Sealey said the audience will be taken on an "exquisite journey of discovery inspired by the wonder of science".

She added: "Both Hawking and McKellen in their narrative talk about what we all need to remember: don't just look down at your feet, look at the stars, be curious."

Her fellow artistic director Bradley Hemmings said the team approached Prof Hawking towards the end of 2011.

'Prudent budget'

"We worked very closely with Prof Hawking to develop a series of messages which are very much integrated into the storytelling of the ceremony.

"We have spent time with him [Prof Hawking] in Cambridge and have been so incredibly gratified with him giving his time".

Sealey would not revealed the cost of the event, but said it had been put together on a "prudent budget".

Speaking before the ceremony, Prime minister David Cameron said: "The Olympics made us proud but I think (the Paralympics) will make us prouder still... It's been a sell-out and I think that's a great story for our country.

"Really what it's about is the inspiration that it gives to a generation of young people.

"And also I think with the Paralympics - even more powerful than the Olympics in many ways - it changes people's minds about what disability is about and what disabled people can achieve."

About £27m was spent on Oscar-winning director Danny Boyle's spectacular Olympic opener, with the remaining £53m divided between the Paralympic opening event and the closing ceremonies for both Games.

Lord Coe, chairman of Locog, said the ceremony will be a "great showcase of the skills and excellence of disabled artists".

"The London 2012 ceremonies are truly global events, with billions of people across the world watching the four shows. This is undoubtedly a fantastic opportunity to showcase talents to the world."

Hopes are high that ParalympicsGB will emulate the success of TeamGB, but one of the UK's most decorated Paralympians has warned the competition for medals is likely to be tougher than ever.

Baroness Tanni Grey-Thompson, who has won 11 Paralympic gold medals, said overseas athletes will want to beat a British competitor on home soil.

"Most countries are envious of the support and funding our athletes enjoy but ParalympicsGB have been preparing well and will give everything they can to win all the medals they can," she added.

Britain finished second in the medals table at the 2008 Games in Beijing, winning 42 golds, 29 silvers and 31 bronzes. China were top with 211 medals, of which 89 were gold.