“I don’t have any memory of who they were,” he said. “Someone saw what happened and called the police.”
Mr Rickman’s mobile phone and keys were stolen in the incident.
The Leeds University graduate, who has worked in numerous communal roles, said support from family, friends and colleagues had been “unbelievable — committee members from all organisations have got in touch”.
A Metropolitan police spokesman said "no arrests" were made. "Detectives from Colindale are investigating the circumstances," he added.
"Anyone with any information is asked to call Detectives at Colindale on 101 or anonymously through Crimestoppers on 0800 555 111"