Good luck to Sue Strachan from Herefordshire who is running for Alzheimer's research.

Sue, 62, was diagnosed with vascular dementia three-and-a-half years ago. She was told by her doctor that keeping fit and exercising could help manage her symptoms.

Read Sue's story, how using the Couch to 5k app helped her to start running and why she wants to "challenge perceptions" of those with dementia.

Half an hour to go until the Queen gets the mass start under way.

How are your nerves, runners?!

Get stretching!

Marcel Hug lost out to David Weir in last year's men's wheelchair race in a sprint finish and is the biggest threat on paper to Weir again this year.

The Swiss is reigning Paralympic champion and has twice won on the streets of London.

He's just hit the front of the leading group but there's still plenty of men in contention at this stage.

We're expecting this men's race to finish around 10:30 BST, give or take five minutes.

Defending champion Mary Keitany is snapping at the heels of the male pacemakers as she opens up a gap from the rest of the field.

Tirunesh Diababa is right on the Kenyan's shoulder, though.

Here's how they got started...

Very much the case of all the gear but no idea for Radio 1 DJ Dev.

Let's hope he makes it to the start line on time...Good luck!

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Jonathan Wood: I'm inspired every year by the London Marathon - it always gets me. Feel the need to do another ... I hope all participants enjoy the day.

Matt Tyler: Good luck to all those running today. Let your training pay off and I hope you all raise lots for chosen charities. Most of all enjoy it, it’s a great marathon with overwhelming support all the way around.

Emmie Vernon: A huge GOOD LUCK to those taking part in the London Marathon today, you are incredible human beings.

Here are the elite women who could find themselves with a podium spot later today.

• Mary Keitany (Kenya) - The 36-year-old is looking for her fourth win in London, having set a women's record of 2:17:01 last year. Keitany will run with male pacemakers in her bid to beat Paula Radcliffe's outright marathon world record of 2:15:25.
• Tirunesh Dibaba (Ethiopia) - The triple Olympic track champion won the Chicago Marathon last autumn and was runner-up to Keitany in London in 2017.
• Gladys Cherono (Kenya) - Cherono is racing in London for the first time but is a two-time champion in Berlin.
• Vivian Cheruiyot (Kenya) - After switching from track racing, Cheruiyot ran her first marathon in London last year at the age of 33. She finished fourth overall and picked up the Frankfurt title in the autumn.

Image source, Getty Images

The women's elite race is GO.

Want to know a bit about the favourites for this race?

Stay tuned...

Image source, Reuters

Paula Radcliffe
Women's marathon world record holder on BBC One

I think there is a big threat to my record today, not just from Mary Keitany but also Tirunesh Dibaba. Between the pair of them they have the strongest shot so far.

I think Mary tried to break the record in New York and went out quickly, but paid the price, because you can't do that in New York. But here in London if the timing is right, she can really win this race and set a new record. It will be interesting to see how it plays out - they could be watching each other or they could push each other to get their best time.

Here's how the wheelchair race got started.

Up next: the elite women!

Baroness Tanni Grey-Thompson
11-time Paralympic champion on BBC One

It's a very strong possibility both the men's and women's records will go today, especially with a pack this size because it means they all maintain higher average times.

We're just over 10 minutes into this wheelchair event and in the men's race defending champion David Weir is tucked in behind the leader. He is going for an eighth London Marathon title.

They're currently well inside course record time in fine conditions for wheelchair marathon racing.

There's a big pack at the front of the men's race while Manuela Schar has a slight lead in the women's race.

There's a familiar face among the competitors in the T53/54 men's wheelchair race.

David Weir became the London Marathon’s most successful ever champion in 2017 when he clinched a record seventh victory.

And now the 38-year-old former Paralympic champion returns to add another medal to his incredible haul.

As in previous years, Weir has some stiff competition for the title.

Switzerland's reigning Paralympic champion Marcel Hug has won the London crown twice and finished just one second behind the Briton last year.

Course record holder Kurt Fearnley of Australia also competes, along with South African Ernst van Dyk, who is a 10-time winner in Boston.

Image source, Getty Images

Paul: Wishing Jackie Robb (Runner 36661) and the 40k others all the best in today's London Marathon. You've worked so hard now enjoy it

Anon: Would love to see an interview with Royal Marine Colonel Simon Chapman running his 10th marathon in 10 days. Bib 27234

Gem: My 70 year old Grandad is running the London Marathon today to raise money for Kidney Research in memory of my Gran.

T11/12 - Para-athletes with a severe visual impairment who usually run with a guide.

T13 - Para-athletes with a visual impairment meeting the minimum criteria (men's race only)

T42/43/44 - Para-athletes with lower and upper leg impairments such as amputations. Competitors race without wheelchairs (men's race only)

T45/46 - Para-athletes with lower and upper arm impairments such as amputations (men's race only)

T51/52 - Wheelchair racers with activity limitation in both lower and upper limbs (men's race only)

T53/54 - Wheelchair racers with partial trunk/torso and leg function.

Image source, Getty Images

The World Para-Athletics Marathon World Cup athletes are also under way in London.

Here's who to look out for...

Image source, .

Image source, .

Tom Gayle
BBC Get Inspired reporter at the finish line

It may seem like a long way off to those running today, but here is the finish line.

Expect to see tired runners, sighs of relief, high emotions, tears of joy and embracing hugs at this spot later on.

Image source, BBC Sport

There are 19 athletes in total in the women’s wheelchair race - and the course record holder is one of them.

Manuela Schar of Switzerland secured her first London Marathon victory 12 months ago and is back to defend her title.

But can she fend off her American rivals?

Seven-time paralympic champion Tatyana McFadden was ruled out of last year's race after undergoing an operation but she previously won four London crowns in a row between 2013 and 2016

Two-time winner Amanda McGrory placed second in Boston, London and Chicago in 2017 before taking third in New York.

Image source, Getty Images

There goes the klaxon...and we're off!