Here's where that viral defiant meme about the London attack came from

People are reacting to the Westminster terror attack by sharing memes of hope and defiance.

One image that is doing the rounds is a London Underground sign bearing the words "We are not afraid."

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The simple but powerful message was also reiterated by Prime Minister Theresa May during her emotional address to UK Parliament on Thursday morning:

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The image was created following the July 2005 London bombings, in which four suicide bombers killed 52 people across the capital.

Hours after the bombings, people from all over the world started posting tributes and artwork on the website We're Not Afraid (which now appears to be defunct).

As the Guardian reported, the images ranged from the Underground logo with "Still not scared" superimposed to "sleeping dogs and cats with the phrase 'I am not afraid.'" Some images had a humorous nature, like the mockup of Osama bin Laden sitting in the road in front of the number 8 bus to Victoria.

The site was set up by Alfie Dennen, a 29-year-old London web designer and mobile phone consultant.

One week after the attack, a Londoner printed stickers with the "We are not afraid" slogan and rode the Tube, giving them out to hundreds of passengers.

"The passengers to whom I gave them, and the numerous London Underground staff and police on duty, were universally willing to wear them; a contribution to a day of solidarity for Londoners of every creed and walk of life," the artist wrote on Flickr.