Hardly. Average speed for the Paris marathon is about 6mins/km or 10kph. And that's people fit enough to be able to actually run a marathon, most of whom have substantially trained for the event, so not the average joker off the street that prepped for "a couple of months".

The fastest female runners are running at 18kph. That's Olympic standard. The average female marathon runner runs at about 9.3kph.

Only competitive male runners would be capable of beating that pace.

Edit: Disclosure - female, and I run a half marathon in two hours That's 10 minutes faster than the average woman and around about average for the entire field. To achieve that time I play an active sport, and train for longer running events (I'm the fastest long distance runner in my sports club). In kph I manage a bit less than 11, which is a long way off 14kph.

For some locations and travel distances I'd not disagree with you, but there is more to factor in here.

What distance is that 9mph over? My running ability has jumped from "can't even face 2km" to "5km in less than 23 minutes most of the time" (PB:21m53s) in about six months due to a new found attitude to health+fitness, but that is still less than 9mph so that sort of rate is going to be a short distance sprint. My 10Km pace (PB:46m21s though minutes or two more than that us more usual) is below 8mph. While I'm sure most average people could match or better my achievements here, I doubt most would want to bother!

What about recovery afterwards? When I run into the office there is a cool down period (basically walking about or lounging until I stop actively sweating) followed by a shower and getting dressed. They don't want me in the office caked in sweat and smelling as you'd expect from that! If I take the 10KM-ish route that makes the whole affair more like 75 minutes than then the less-than-50 I'm running and for my 5KM-ish route the recovery and shower time is longer than the running time so effectively halving my pace without even considering any warm-up time before I hit the pavement with a vengeance.

Also running every day is not recommended unless you are only doing a short distance, unless you are trying to wreck your joints, no matter how good your shoes are. Of course you could switch "run+recover+shower" for just walking the distance both ways every day and use up about the same amount of time, and for many people that might beat the car or public transport based commute if they gave it a try.

Cycling (including the public cycles that exist in London, depending how the hire costs compare to the op-front and running costs of your own kit) are probably a better idea than running though some of the above would count for many people there too.

Exercising in London pollution is probably a bad idea.

http://www.bbc.co.uk/news/uk-england-london-33536989

http://www.bbc.co.uk/news/uk-32233922

In european center cities, car mean speeds are usually <= 12mph (<20 km/h). You can get faster on a bike if you are made confortable enough to do this (it boils down to bike infrastructure).