Early afternoon, one day later, Westminster Bridge.
Both ends have been sealed with white tape, which flaps feebly in the wind. Normally the silhouette of the bridge has vehicle sized humps, and tiny people rushing by, but today's it's flat. Occasionally the cordon is detached to allow officialdom to pass through, but ordinary people are held at bay by a polite stare, and advice on the best route for negotiating round the disruption.
Tourists are streaming back to visitor attractions on the Albert Embankment, brandishing their tickets to the London Dungeon, milling on the steps into the London Aquarium and stuffing themselves with a Big Mac in lieu of lunch. The London Eye is turning again, with queues undaunted by yesterday's extended spin. Foreign camera crews are poised by the river's edge, explaining to the audience back home what's going on, with Parliament framed on the horizon.
On the north bank a police officer reels in the plastic ribbon blocking the Cycle Superhighway as a flow of pedestrians streams by. Initially only a few cyclists notice, while one young man on a motorised skateboard takes advantage of the off-peak conditions to whirr by, headphones poised. Road traffic is extremely light - a lone taxi, a delivery van for a small catering company, a limo.
Outside the new New Scotland Yard, a larger media circus is in evidence. The Queen was supposed to be here today to open the place, a small item at the end of the news, but instead the exterior is the focus of far wider attention. Only now are the public being allowed into, and out of, Westminster station, where the number of armed officers in the ticket hall almost exceeds the number of customers.
There's still no access to the nearest corner of Parliament Square, so police and journalists cluster on the Embankment traffic island. But Westminster Bridge is open, freshly reopened, and virtually empty. All the cars and buses that had been sitting here since yesterday afternoon have been cleared, along with all the evidence that this was ever a crime scene, and the span has the emptiness film producers can normally only guarantee at five in the morning.
For the few tourists who've managed to arrive at precisely the right time, the perfect selfie can be framed. Many of them won't even realise how hard it is normally to snap the Palace of Westminster without a horde of people in the background doing the same thing. The tourists doing the same thing 23 hours earlier managed to arrive at precisely the wrong time. Their snatched videos went round the world, if they were lucky,
In a few hours there'll be bouquets, but until then nothing marks the places where, who knew, it wasn't safe to stand. Where bodies lay, where bystanders ran to help, where hastily erected tents shielded the worst of the injuries from view, there's now just tarmac painstakingly swept for evidence, then tidied up, then cleaned. A couple of cars pass by, on the road of course and not on the pavement, and who would ever have assumed the opposite?
It takes some imagination to picture this walkway as a inescapable trap, with a line of traffic on one side and the edge of the bridge on the other. Only now is it blindingly apparent how low the parapet is, barely at chest height and all too easy to be manoeuvred over. The waters of the Thames are choppy, and not as far down as you might expect, though far enough at speed. On one of the lampstands a knot of police tape remains.
The souvenir kiosk at the eastern end of the bridge remains shuttered. A rack of printed merchandise has slumped onto the pavement, with most of its pockets empty, and the postcards in the others askew. Larger canvases depict the bridge at an unlikely angle, with one red bus prominent on each. The message on the final board is normally a cliche - Keep Calm And Carry On - but today that's precisely what Londoners have done.
As cordons clear, a stream of cars, vans and buses arrives. The bridge begins to look ordinary again, or at least will do once the chestnut sellers and card sharps have returned to their pitches. Every effort has been made to return this part of London to normality, a state impressively reattained in less than 24 hours. An unspoken message has been sent out to the rest of the world that whatever you may choose to do to our capital city, life goes on.
One day we'll be able to cross Westminster Bridge without thinking back to what happened here. We do the same in many other parts of London, the memories of the tragedies that played out dampened by years of familiarity. For now however it's impossible to walk across without feeling the shadow of events cast before you, and pondering what if, and why here, and why? And because it remains impossible to stop a maniac with a car, where next?