Speaking at the Future Parks conference in London last week organised by the National Trust (NT), social sector financial advisers Social Finance and law firm Winckworth Sherwood, Ghosh revealed results of NT-commissioned natural capital analysis of Sheffield's parks by Vivid Economics, which formed part of the 18-month Rethinking Parks project.
The project found parks provide benefits worth nearly £1.2bn, rather than the liability of £16m a year according to conventional public accounting. For every pound spent on public parks, society receives £34 of services, the study found, while around 60 per cent of the benefits of public parks in a large city arise from their contribution to physical and mental wellbeing.
"We think we can make a clear business case for parks in that way my former colleagues at the Treasury will understand," former senior civil servant Ghosh said.
At the event, NT, Social Finance and Winckworth Sherwood launched an online toolkit at www.futureparks.org that offers a 'People's Parks Trust' exemplar to follow or adapt as well as advice on considering and establishing a parks trust. The exemplar is a blended financial model, with an element of endowment and private enterprise, similar to how the National Trust operates, Ghosh said.
"We are only able to operate as we have a permanent endowment, we have enterprises, we are reliant and benefit enormously from volunteers and permanent members of staff. It was that kind of mixed mode that emerged with our People's Trust."
The Milton Keynes Parks Trust was established in 1992 with a £20m endowment and a 999-year lease from the local authority. Its income is mostly from £90m of commercial property and £40m equities and its endowment is now worth £130m.
Chief executive David Foster said: "A lot of people look at Milton Keynes Trust and think it's a wealthy organisation, it can't possibly fail. When I arrived 15 years ago all the talk was about how long have we got before we start eating into our capital.
"And once you start doing that's it's a slippery slope. Now after lots of imaginative work and adventurous investment plans and ideas we talk about when will we get to the happy point of when we will be financially sustainable, we don't talk about when we are likely to go bust."
Foster's advice is to "try not to pick and mix. I just encourage you to be bold, to be courageous. People don't mind who owns the parks, it's a bit of a myth that they feel that they should be in public ownership. There are some people who feel very strongly about this and if you start down this route you will find out they will come out from all over the place."
Sharing experience of a newly-created not-for-profit social enterprise was managing director of Enable Leisure and Culture, Paul McCue, who helped led the creation of Enable, which pays Wandsworth Council to manage concessions in 34 parks, 22 playgrounds and 450 allotments, alongside culture, on a four-year contract, on agreement it would find £1m in savings.
The council still pays for a grounds maintenance contact directly. Enable allows McCue to keep income from events. He advised: "Start early, take expert advice, be prepared for the switch from colleague to contractor and manage expectations."
At the start of the process is Newcastle which is exploring transferring parks to an independent body with cooperative and mutual values, which started with the question: 'Could we have an NT for Newcastle?'
Digital Newcastle assistant director Tony Durcan said the authority has lost 91 per cent of its budget since 2010/11 and has to find a further £70m in cuts by the end of the decade. "We're retrofitting transformation," he said.