Bosses at Harrow Council took the unusual step of asking football fans to be on the lookout.
ITV News London's Chris Paxton is taking part in the Clipper Round The World Yacht Race. The race fleet have just visited Hong Kong.
Sunny spells between the showers. Highs of 10C.
Speaking to the Evening Standard, Zeba Begun, whose house overlooks the scene where the woman died said:
"She then looked to her left and then to her right and I had no idea what she was going to do, I thought maybe she was joking about, but then about 30 seconds later I heard some beeps from the oncoming traffic which could see her.
"And she just waved at the traffic and then fell down onto the road. As soon as I saw it I called the ambulance and police."
The man arrested in France has a motorcycle helmet similar to one in an e-fit issued by police, according to a French broadcaster. BFM claimed the man lived alone in the mountains and was found with arms in his home.
In November, police released an image of a male motorcyclist they wanted to speak to in connection with the killings. at the time the helmet was said to be "very particular" and one of only a few thousand models worldwide.
Police are currently searching the house of the man arrested as part of the investigation into the deaths of four people in 2012, in village near Chevaline.
The French prosecutor has said the man is not a suspect at this time but is being questioned because he resembles an e-fit and was in the area at the time of the killings. He could be released as early as this evening.
Sources close to the probe have told ITV News that the arrest is a result of the photofit released in November. The arrest is the first of a number of the arrests and is believed to be critical to the investigation, the sources said.
In November, police released an image of a male motorcyclist they wanted to speak to in connection with the killings.
The French Gendarmerie released an artist's impression of a motorcyclist who was seen riding in the area shortly before the four murders took place.
The man's helmet was said by Mr Maillaud at the time to be "very particular" and one of only a few thousand models worldwide, with a bottom section which opened laterally to reveal the lower face.
Read more: Man arrested over Alps killings
Police in the UK have confirmed the arrest of a man in France in connection with the murder of four people in the Alps.
British engineer Saad al- Hilli, his wife Iqbal, her mother Suhaila al-Allaf and French cyclist Sylvain Mollier were all killed in the attack on September 5 2012.
In a statement Surrey police said:
"Surrey Police can confirm that an arrest has been made in France today in connection with the murders of four people near Annecy, southern France in September 2012.
"The arrest has resulted from a line of enquiry in France and is not as a result of the investigation carried out in the UK."
A 48-year-old man has reportedly been arrested by French police in connection with the investigation into the murder of four people in 2012.
On 5th September 2012, Saad al- Hilli, a British engineer, his wife Iqbal, her mother Suhaila al-Allaf and French cyclist Sylvain Mollier were all killed in the attack on September 5 2012.
A406 NCR W/B / Crooked Billet - remains closed W/B; police incident. Tbacks beyond Redbridge Rbt. E/B re-open, but Tbacks to Finchley Hi Rd.
– Metropolitan Police
Police were called to reports of a female believed to have fallen from a bridge on the A406 close to the junction of the Billet Road roundabout, Walthamstow, at 14:27hrs on Monday, 17 February.
London Ambulance Service and London's Air Ambulance attended. The female was pronounced dead at the scene.
Next of kin are yet to be informed.