Dashcam footage has captured the shocking moment a would-be thief tries to steal a bicycle from the back of a car - while it briefly stops at a red light.
In the one-minute clip, dated 3:24pm on Sunday, a man wearing a hoodie is seen cycling behind the car as it is travels down Tower Bridge Road in central London.
When the car stops at a crossing, the cyclist seizes his opportunity, and starts to remove a racing bike from the rack at the back of the vehicle.
But time is against him. As the lights change, the car accelerates, leaving him struggling to keep up.
As the car speeds off, a man is seen chasing after the thief in the background.
The incident was captured by Musa, 24, the owner of the car, who works in communications. He had been travelling home after going on a long bike ride - when the thief decided to target him.
His girlfriend Chloe, a 24-year-old trainee solicitor, was driving the car at the time.
She told MailOnline: 'Musa is doing the London Revolution bike ride this weekend, so he'd just finished 80 odd miles that day. I picked him up from Lee Valley and we were driving down Tower Bridge Road.
'There were quite a lot of traffic lights so we kept stopping and starting. When I noticed a guy cycling along behind me, I thought he he was a bit close to the back of the car. But I just thought he was being silly - because if I had to brake, then he was going to hit me.
'I thought: well he can do what he likes - he's only putting himself in danger.
'The next thing I knew, we were at the last set of lights before you accelerate onto the dual carriageway, and I heard a beep from the car behind us.
'As I looked into my rear view mirror, that's when I saw the cyclist twiddling the top fastening of the bike. Just then, the light went green so I started to accelerate.
'From what I could see, the bike was still attached - so I decided to carry on because I knew he wouldn't be able to keep up with the car.
'He tried to chase us for quite a while before giving up. Then, once we'd got a few hundred yards down the road, I pulled over because I could see the bike was slipping.'
When she got home, Chloe watched her boyfriend's footage of the incident and sent it to police.
She believes the attempt to steal the Mekk Primo carbon road racing was planned.
'I think he'd been watching from somewhere - probably because he knew there were a lot of traffic lights and I'd probably have to stop.'
Musa, however, couldn't bring himself to watch the footage.
'I think he was really disappointed because he's worked hard to get that bike and really enjoys his races. And he's had a couple of normal bikes stolen already.'
The couple hope that someone will be able to identify the thief from the film.
'The focus for us is to try and catch the guy - but we also want to warn other cyclists and car owners to be vigilant,' said Chloe.
'Musa has a lot of cycling friends who would be similarly gutted if their racing bikes were to be stolen.'