The July 7 bombers who targeted London’s transport system were seen by witnesses laughing and smiling hours before the attacks, an inquest has heard.

The four men were spotted looking relaxed as they travelled by train to the city with backpacks full of explosives to commit mass murder in 2005, it emerged yesterday.

Hugo Keith QC, counsel for the inquests, read out the names of the 52 commuters who were killed when the four British Muslim bombers detonated devices on board the three Tubes trains and a double-decker bus at the start of the inquest.

After a minute’s silence at London’s Royal Courts of Justice in memory of the victims, Keith said the attacks targeted British nationals as well as foreigners “with no regard to whether the victim was Christian, Muslim, a follower of any of our other great faiths, an adherent to none”.

“They were acts of merciless savagery which could only outline the sheer inhumanity of the perpetrators,” he added.

The inquest, which is expected to last five months, was also told how the bombers might have planned to act 24 hours earlier – the day London was awarded the 2012 Olympic Games.

Ringleader Mohammed Sidique Khan sent a text message at 4.35am the previous day cancelling a meeting with another of the bombers due to a ‘major problem’.

He told Shehzad Tanweer: “Have major problem. Cannot make time. Will ring you when I get it sorted. Wait at home.”

Khan then visited Dewsbury Hospital with his wife, Hasina Patel, on July 5 because of complications with her pregnancy. She miscarried the day of the attacks.

Keith told the inquest: “It may have been that the attack was originally planned for a different day.”

Bereaved relatives of the victims killed in the explosion later wept in court as they heard how emergency services struggled to cope after the bombers struck.

Audio recordings of calls to London Underground controllers speaking to emergency operators were played to the coroner.

They revealed that 42 minutes after the blasts, key staff were still denying terrorist involvement.

As the reality set in, a supervisor at Aldgate called London Underground, urging: “Will you please get as many ambulances as you can here.”

Coroner Lady Justice Hallett heard the four bombers – Khan, Tanweer, Jermaine Lindsay and Hasib Hussain – committed the atrocities will the intention of getting worldwide publicity.

Ros Morley, whose husband Colin died in the bombing of a subway train near Edgware Road, said she hoped the inquest would reveal whether mistakes had been made.

“Innocent citizens in the UK and worldwide need to know that they are protected now and in the future,” she said.

“I hope it is possible to gain something positive out of a deeply tragic event in which 52 innocent people lost their lives.”

Graham Foulkes, whose 22-year-old son, David, died in the Edgware Road blast, said listening to the “chit chat” of the emergency calls “made us all feel very sick”.

“It’s become clear they were completely unprepared and didn’t know how to respond,” he said.

The inquest continues.