More than 80 condolence books created following the 7 July London bombings have been archived.
The books will be available to consult online
The volumes with messages of sympathy were collected following the suicide attacks in which 56 people died.
The books, including 12 from abroad, will be stored by London's Metropolitan Archives (LMA) in their Clerkenwell vaults.
The LMA is the UK's largest local record office, with 1,000 years of records kept on 45 miles of shelving.
Many of the messages, which will be available online, were left by commuters across London while others were sent in by churches, schools and shops across the UK.
Entries include messages from around the world including Canada, the US and Australia.
"We share the grief of your loss because it is also ours," wrote Jeff Booton, a German visitor to Coventry Cathedral.
"The love and confusion which survives can never be destroyed."
Deputy Mayor of London Nicky Gavron said the books "will play an important part in helping us remember how London pulled together in those difficult times".