Inspiring messages appear at London Underground subway stations after attack "You have to be at your strongest when you're feeling at your weakest."

London -- Londoners returned to work Thursday morning after an attack in the heart of the city yesterday left four people dead, including the assailant. While most faced a more visible police presence along their commutes, some Londoners were also greeted with messages of resilience at train stations within London’s subway system, known as the Tube.

The message board at one station near the Tower of London, just 2.5 miles from the site of the attack, reminded commuters that, “The flower that blooms in adversity is the rarest and most beautiful of all.”

The London Tube system has a longstanding tradition of posting quotes or inspirational messages on whiteboards inside stations around the city. With more than a billion journeys made on the Tube in a year, the message boards are a highly visible means of communication with commuters.

Leicester Square, one of the busiest stations in Central London, posted the following message:

Another station in West London asked commuters to focus on the strength that ordinary people have in the midst of adversity. “Bad things do happen in the world … but out of those situations always arise stories of ordinary people doing extraordinary things,” read the message board.

The Oval station in South London offered its condolences to the city with the slogan, “You have to be at your strongest when you’re feeling at your weakest.”

Another South London station shared a story from Fred Rogers, known to generations of children as the face of Mister Rogers' Neighborhood. “When I was a boy and I would see scary things in the news, my mother would say to me, ‘Look for the helpers. You will always find people who are helping.’”

The messages have been shared widely on social media, where they’ve resonated with grieving Londoners.