LONDON - More than 200 survivors were allowed back inside Grenfell Tower in London on Thursday to help them comprehend the scale of the disaster as the British capital marked the first anniversary of the deadly fire.

Mental health therapists, police and ambulance crews accompanied residents who wanted to return to their flats. They had asked to see where loved ones perished, collect mementos or "say goodbye" to their former home.

A total of 223 people escaped the blaze a year ago, while 72 were killed.

About 5,000 people are estimated to have taken part in a silent walk in London in memory of those killed in the deadly fire.

Firefighters laid down their helmets and formed a guard of honor as the marchers, who were carrying banners and wearing green, passed by.

Details of the visits emerged Thursday as the lead National Health Service (NHS) mental and community health trust for Grenfell said it was preparing to offer help to victims for another five years.

Former residents, often supported by friends, were given protective suits and breathing masks as they were led up the stairs. Some went as high as the 23rd floor. Items that could be saved were decontaminated before being returned to their owners.

Local authorities said its outreach teams had contacted 6,821 people affected by the disaster.

Almost 1,700 identified as having an urgent health need have been screened for post-traumatic stress disorder, of whom 720 had started to receive treatment.