“Exit here for Westminster Abbey and the Houses of Parliament.”

During the Thursday morning rush hour on London’s Jubilee Line, that pre-recorded invitation did not apply. The previous afternoon, a pathetic thug had driven a car at high speed into a group of schoolchildren and other pedestrians on Westminster Bridge.

From that moment, the lives of the families of the victims of his random hatred were devastated.

While the police inspected the crime scene of his murderous rampage, Westminster Tube station was closed. It soon returned to normal. But while the perpetrator presumably hoped to divide us, his appalling act of cruelty will have the opposite effect.

Consequences there will be, though — starting with an abatement of the crowds that flow between the South Bank and Westminster.

The last time the river crossing eulogised by Wordsworth achieved so high a profile on screens globally was during the London Olympics in 2012. The Marathon celebrated the best of humanity, and revealed the capital at its best; five years later, the world watched, horrified, at the carnage caused by the worst of humanity.

Some will conclude that, however strong their appetite for a visit to London, the potential risks outweigh the rewards. An understandable view, given the horrific images of suffering — though statistics tell an entirely different story

Agreed, the ridiculous fanatic who caused such trauma was one of us. Yet Britain is an overwhelmingly safe and benign nation, where the numbers on everything from nasty diseases to road safety are about as good as they get.

Perceptions, though, are powerful. London has the built-in advantage over other capitals of being easiest to reach, having more airline seats pointing at its six airports than any other city, as well as trains from Brussels and Paris rail link on Eurostar. But the proportion that are occupied is likely to dwindle in the short term after the tragedy — just as it did on the cross-Channel rail link after the attacks in the French and Belgian capitals.

“Anxiety obstacles for fringe travellers” is the clinical term to describe awful events such as terrorist attacks that deter some prospective visitors. The London hotel trade, as well as the wider tourist industry elsewhere in Britain, can expect a downturn in demand.

People who live in much more dangerous locations will follow their hearts, or rather allow their hearts irrationally to persuade them to remain right where they are.

Even the ensuing price cuts will not lure the fretful: the very last thing they want to do right now is “Exit here for Westminster Abbey and the Houses of Parliament.”

So the enlightened traveller will deduce that now is a great time to visit London. Pragmatically, the crowds at the great (and free) cultural attractions will dwindle along with room rates. Emotionally, the benefits are much greater. As with Paris and Nice, Brussels and Berlin, the city will welcome strangers more warmly than ever.

I am writing from Istanbul, a city that has endured more than its fair share of tragedy in recent times. The Foreign Office warns: ”Further attacks are likely and could be indiscriminate.” And yet I have never felt more at ease in the city, knowing that 15 million good people are watching out for my welfare.

Tourism to Turkey slumped by one-quarter last year, and the figures for January show a further 10 per cent decline on 2016. Which helps explains why my air fare was less than I paid when first I first flew here in 1989, and wrote the very first 48 Hours in our city-break series.