Dr Singer, born in 1948 - the year the NHS began - was a committed trade unionist and chaired the Doctors in Unite union for many years.
In a tribute posted on the Doctors in Unite website, he is remembered as 'passionate, principled and loyal', and an 'uncompromising defender of the NHS as Nye Bevan intended, a comprehensive health service, free at the point of delivery, publicly funded and publicly provided for all'.
In a 2014 interview with GPonline to mark the founding of the organsation - known then as the Medical Practitioners Union (MPU) - he explained the philosophy that underpinned his approach to medical politics.
'You have to be on the streets,' he said. 'You have to bring your colleagues to a point where they can see that unless they act collectively and in a fairly visible manner, the plight of general practice will not be recognised.'
Dr Singer, a GP in Edmonton, north London for over 25 years, campaigned powerfully - and visibly - for the NHS he believed in well beyond his retirement from frontline general practice.
In 2012 as then health secretary Andrew Lansley toured a north London hospital as his controversial health reforms went through parliament, Dr Singer confronted him in person, saying: 'I am a doctor of 30 years Mr Lansley, explain to me how this is going to make patients better.'
A year earlier, Dr Singer was blocked by police from delivering a letter to Mr Lansley as part of a protest outside the health department's Whitehall headquarters.
In general practice, Dr Singer believed that the profession was disempowered by independent contractor status - and felt that a shift to a fully salaried service, with doctors represented by a strong union would empower the profession to stand up better to the pressures of rising workload and demand and underfunding.
Fellow east London GP Dr Jacqui Applebee wrote in a Doctors in Unite newsletter: 'We were deeply saddened to hear of the death of our wonderful friend and comrade Dr Ron Singer. Tributes have been pouring in. It is very hard to encapsulate such a fantastic human being in words. Ron was an inspiration to so many people.'
The Unite union confirmed that Dr Singer died after a heart attack at home on 28 May.