Four men, wearing smart suits and towing suitcases on wheels, crossed the road near Leeds railway station and did a double- take: they had just glimpsed two police officers patrolling with their fingers close to the triggers of very large guns.
This is the new reality of Leeds, which until 6am on Tuesday was aware of the horror of last week's attacks in London but a long way from it. Now the city will be known as the home of the first British-born suicide bombers to detonate themselves in their own country.
"One-way ticket to slaughter" was how the front page of the Yorkshire Evening Post summed it up.
West Yorkshire chief constable Colin Cramphorn was slightly more restrained. "[ The events in Leeds and Dewsbury] may give people cause for concern that the threat from terrorism that they thought lay elsewhere in this country is to be found rather closer to home."
You couldn't blame Mr Cramphorn for his careful understatement. But Derek Rawnsley, who has sold the Evening Post on the streets of Leeds for 40 years, was blunter.
"You don't feel safe at all in this bloody country," he said. "You could be standing here one minute and be dead the next. I've sold a lot of papers, but it's a bad way to sell them. I'm surprised this has happened here."
All around him - a few wild police sirens apart - life appeared to continue as usual. They queued at cashpoints and drank coffee outside Starbucks. A mother gave her baby a bottle near Briggate, where the flowers bloomed in hanging baskets. An elderly man honoured the British tradition of wearing stout shoes and socks with shorts.
And the sun shone gloriously, with lunchtimers soaking it up outside Leeds town hall, where only a union flag flying at half-mast was a reminder of murder on the streets of London.
Joyce Smith, who had come from Huddersfield to shop with her daughter, Jane Oates, bought a copy of the London-based Daily Mail to read all about it.
"I won't let this stop me doing what I would have done," she said. "But it's at the back of my mind and I suppose I am being more careful."
Ms Oates then said her mother had wanted to postpone the trip. "I would have preferred it to be another day," admitted Mrs Smith.
"But you have to carry on as normal," argued Ms Oates. "If they are going to do it, they will."
Her mother reluctantly agreed; there had been a bomb scare in nearby Huddersfield that morning, so there wasn't much point in changing plans.
"I'm just sad that [ the bombers] feel they have to do this to their own countrymen. They have been brought up here and been given benefits here and then they do this to us," she said.
Her daughter continued: "You don't know where an attack will happen next. But you cannot stay indoors for the rest of your life."
Anna Kopczak, a 22-year-old student from Poland who had come to Leeds to look for work, scanned the Evening Post, with its reports, pictures and graphics.
"This is my first time in England and this is a big shock for me," she said. "I do not have a television and my parents told me about the bombs in London at 2pm that day. I was scared - but it was in London. Then yesterday my family told me about the terrorists in Leeds. So I have bought the newspaper to get to know all this information.
"My first thought was that I want to go home to my family. When the attacks happened in New York, it seemed like a film or a book for me. It wasn't real, I couldn't believe it. But now it feels close to me.
"The Polish army has been in Iraq so I am afraid there may an attack in Poland. No one can feel safe nowadays."
Karen Wilkinson, newly-graduated from Leeds Metropolitan University, said she had not thought that terror would come so close.
Other people relaxed on the steps of Mill Hill Unitarian chapel, which describes itself as a refuge for everyone: "Called by different names, worshipped in different ways; there is but one God."
In the nearby West Yorkshire Playhouse, the run of the play The 39 Steps, a story of British grit against the forces of evil, continues to the end of the week. The show must go on.