The University of Cambridge graduate was one of two people killed when 28-year-old Usman Khan launched the attack at a Cambridge University conference on prisoner rehabilitation.Khan, who had been jailed for six years over a terror plot, was restrained by members of the public on London Bridge before police shot him dead.
Mr Merritt has been described on Twitter by his father as a "beautiful spirit".
Three others were injured in the attack while the other fatality, believed to be a woman, has not yet been named..
Khan had been one of dozens of people - including students and offenders - at the event.
Neil Basu, London's police counterterrorism head, said Khan was attending a program that works to educate prisoners when he launched the attack, killing a man and a woman and injuring three others just yards from the site of a deadly 2017 van and knife rampage. Basu said the suspect appeared to be wearing a bomb vest but it turned out to be "a hoax explosive device."
Prime Minister Boris Johnson said he had "long argued" that it was a "mistake to allow serious and violent criminals to come out of prison early."
"It is very important that we get out of that habit and that we enforce the appropriate sentences for dangerous criminals, especially for terrorists, that I think the public will want to see," he said.