“A beautiful spirit who always took the side of the underdog.”

That’s how David Merritt described his 25-year-old son Jack, who was stabbed to death in an attack at London Bridge.

A woman who died in the attack – declared by officers as a terrorist incident – has not yet been named. Three others were injured.

A law and criminology graduate, Mr Merritt was a course coordinator for the University of Cambridge’s prison rehabilitation programme.

The project, Learning Together, gives students and inmates the opportunity to study together, to help reduce re-offending – something Mr Merritt had a “deep commitment to”, according to people who worked with him.

A vigil was held in Cambridge, where Mr Merritt was from, on Saturday. His friends, family and those who worked with him have been paying tribute.

‘Too good for this world’

Emilee Hopper, who said she had been friends with Mr Merritt at school, described him as “one of the kindest people I’ve come across and a beautiful soul”.

Daisy Knock said Mr Merritt was “too good for this world”.

“He worked for, and believed in something, that will one day change how we see the world,” she added.

Another friend said the University of Manchester and University of Cambridge graduate was “incredibly witty and intelligent, with more lust for life than many our age and a determination to make his mark in the world”.

Rapper Dave said Mr Merritt was “the best guy” and his news of his death was “one of the most painful things”.

Dave’s Mercury Prize-winning album was inspired by rehabilitation therapy his brother Christopher Omoregie has received while serving a life sentence for murder.

The Streatham-born rapper said Mr Merritt had “dedicated his life to helping others” and it was “genuinely an honour to have met someone like you”.

Dave said he would “never ever forget” everything Mr Merritt had “done for us”.

Meanwhile members of the criminal justice community said they were “in deep shock” over Mr Merritt’s death.

Prison Radio UK said praised the 25-year-old for his help with a podcast that explains the law to prison inmates.

“He was generous with his time and all too happy to help others. His life should inspire us all,” the radio station said.

Legal commentator Joshua Rozenberg interviewed Mr Merritt for the BBC in February when he was working with Learning Together at HMP Warren Hill in Suffolk.

Mr Rozenberg described him as “a fine young man, dedicated to improving people’s lives”.