A post by his daughter, Natasha, here explains the circumstances in depth, but here's a quoted summary:
"Earlier this morning, at 12.40am, my father died peacefully at the National Institute for Neurology, near Russell Square in London.
"It all happened very suddenly, and was mercifully quick. My mother arranged for him to be admitted to hospital on Monday for what everyone had thought would be a brief visit. He had suspected inflammation in the brain.
"My mother and I had the results of the scan which were 'grim' as the consultant explained to us. The tumour had grown substantially.
"As far as I am aware, the last word my father spoke was on Wednesday, was the word "blins". This is a made-up family word that is an expression of happiness, satisfaction and either comfort or delight."
All at DiS would like to offer their sympathies to John's family, those he worked with over many years - many people close to DiS have been in his employment at one time or another - and to any of the bands and fans touched by the music he helped bring to wider audiences. Rest in peace.