Did Dewsbury baby drama delay 7/7 murders for 24 hours?

Ringleader Mohammed Sidique Khan sent a text message at 4.35am the previous day, apparently abandoning a meeting because of a "major problem".

The sudden change of plan was among a raft of extraordinary new information revealed about the 2005 atrocities as inquests into those killed finally got under way.

The inquest heard that Khan visited Dewsbury Hospital with his wife, Hasina Patel, on July 5 because of complications with her pregnancy and she miscarried on the day of the attacks.

Hugo Keith QC, counsel for the inquests, said a mobile phone recovered from one of the bomb sites revealed that Khan texted Shehzad Tanweer the previous day.

The text message read: "Having major problem. Cannot make time. Will ring you when I get it sorted. Wait at home."

Mr Keith added: "It may have been that the attack was originally planned for a different day."

The four attackers also made smaller bombs they could have thrown at police if they had been stopped before carrying out their plot, the inquest heard.

The main devices used in the attacks contained several kilos of homemade high explosives created from a mixture of hydrogen peroxide and pepper and were detonated by a 9-volt battery.

When police raided the plotters' main bomb factory at 18 Alexandra Grove in Leeds five days after the attacks, they found equipment and chemicals scattered everywhere.

Mr Keith lsaid there was no attempt to hide the bombers' "evil work" and it was plain they had no intention of returning.

The inquests heard that the 52 people killed on July were murdered in acts of "merciless savagery" as the long-awaited hearing got under way with a minute's silence.

Coroner Lady Justice Hallett heard that the four bombers - Khan, Shehzad Tanweer, Jermaine Lindsay and Hasib Hussain - committed mass murder with the intention of getting worldwide publicity.

The inquests, being held at the Royal Courts of Justice in central London and expected to last up to five months, began to hear a timeline of the bombers' movements from when they left Leeds at 4am.

Further dramatic evidence revealed today included:

The bombers apparently prepared to fight police if intercepted, carrying improvised bombs, which could be thrown, and a semi-automatic handgun, as well as bomb spares;

A mystery white saloon car and six Asian males were seen to leave a bomb factory in Alexandra Grove, Leeds, by a neighbour but it has never been traced;

Lindsay received a parking ticket as he slept in his car while he waited at Luton station for the other three conspirators. The attendant feared being attacked;

Commuters described some of the bombers as "smiling and laughing and generally relaxed" as they travelled to King's Cross Thameslink on a delayed train;

A piece of paper recovered from inside Lindsay's passport found in a Piccadilly line tunnel mentioned journey times to Paddington, Westminster and Bond Street;

A man resembling Lindsay approached a London Underground employee at King's Cross and said he wanted to speak to the duty manager about something "very important", but disappeared.

The hearing was told that the Metropolitan Police investigation database is the largest ever created and thousands of documents have been considered for the inquests.

The coroner must sift through a deluge of information from police, MI5, other emergency services and eyewitnesses, as well as CCTV, forensic and technical evidence.

Lady Justice Hallett said as much evidence as possible would be considered in public and no decision had been made on whether she would sit in secret when considering sensitive intelligence material.

There have already been a series of investigations into the 7/7 attacks, including major reports by the Parliamentary Intelligence and Security Committee and the London Assembly.

The inquests have a wide-ranging remit to examine whether the emergency services' response was adequate and whether MI5 and the police could have prevented the atrocities.

Opening the inquest, Mr Keith said: "The slaughter caused by the bombs caused not only death, devastation and mutilation but unleashed an unimaginable tidal wave of shock, misery and horror for their families and loved ones.

"Just as the lives of 52 victims were callously and brutally ended, the lives of many others have been and continue to be tormented.

"They were acts of merciless savagery and one could only imagine the sheer inhumanity of the perpetrators."

Mr Keith added: "They detonated amongst the innocent and the unknowing, indiscriminately killing and maiming passengers who were simply going about their daily business.

"The bombs struck down men and women, the old and young, British nationals as well as foreigners.

"They had no regard to whether the victim was Christian, Muslim, a follower of any of our other great faiths, an adherent to none.

"They were just travelling on the London transport system. It is the saddest of duties to open their inquests."