A team of four calling themselves ‘The Merrittocracy’ have raised almost £15,000 in just two days and hope to double that.

They said: ‘We are all devastated by Jack’s death but determined to celebrate him.

‘Jack was proud. Jack was absorbingly intelligent. Jack was fiercely loyal. Jack loved music, art, eating good food with his family, and having more than one pint with his mates.

‘And on that point we, his friends and family, are going to throw one hell of a celebration for him. Because my god, did that boy know how to party.’

Jack, 25, was fatally stabbed by convicted terrorist Usman Khan on November 29.

The Cambridge University graduate, from Cottenham, Cambridgeshire, worked for Learning Together, an organisation bringing together prison-based students with university students to share learning and experiences.

The scheme was holding a fifth anniversary event at Fishmongers’ Hall when Khan launched into his attack.

Volunteer Saskia Jones, 23, also died in the attack.

Khan was convicted in 2012 for terror offences after joining a cell which planned to bomb the London Stock Exchange and train British terrorists in Pakistan.

He was released on licence in December last year after serving less than half his sentence.

The fundraisers said all additional money raised by the Gofundme appeal will be donated to Jack’s legacy, which is understood to be his passion for prisoner rehabilitation.

‘We are raising money for a celebration of Jack’s life. All the things he loved – for his closest friends and family.

‘We will keep costs to a minimum. Services will be provided free or discounted where possible. All additional money will be donated to Jack’s legacy.’

‘This is not the end, this is a beginning.’