Claire Lomas, 32, who was paralysed from the chest down in a horse riding accident five years ago, is not due to finish the course until a week today.
She is expected to finish within 40 hours, spread over 17 days, moving at about half a mile an hour.
She is wearing a high-tech power suit, developed in Israel, which helps her walk unaided, with her arms taking most of the strain.
She is the first person in Britain to wear the suit. However she needs support negotiating London’s dodgy pavements.
It’s a gruelling effort for the competitor, who has battled through London’s downpours, and found it tricky to negotiate buckled pavements and insulation-covered power lines.
But she has the support of her family who are joining her in shifts, including her husband Dan, a research scientist she met a year after the accident, and her 14-month-old daughter.
Kenyans Wilson Kipsang and Mary Keitany won the men’s and women’s groups on the Marathon on April 22, in just over two hours.
By the time Lomas had reached the one-mile mark, the marathon organisers were beginning to pack up.
But it hasn’t dampened her spirits. So far, Lomas has raised £48,000 for spinal research.
‘It’s been amazing since the start,’ says Claire. ‘The crowd went mad when I made my first step — it’s a moment I’ll remember for the rest of my life. For the first three-quarters of a mile, they were shouting and encouraging me. People were chucking money out of windows.’
The £43,000 contraption she wears stretches down either side of her chest to her calves. When she leans forward, pressure pads in the 35kg suit send messages to battery-powered motors. An upper motor moves her hips and a lower one bends her knees. A black fob strapped to her wrists acts like a remote control, ordering the suit to sit, stand, walk or negotiate stairs.
Every evening Lomas has intense physiotherapy and her legs are checked for injuries she hasn’t felt.
Claire decided to do the marathon a year ago, and has been training since January, with the help of a standing frame and an adapted exercise bike. She has also been skiing on a sit-ski, a seat precariously attached to a single ski.
As well as following her sporting pursuits, and bringing up her daughter, Claire has a jewellery design company, trains people in event and cross-country riding, and is planning to write a book.