The Royal Parks charity has insisted that an "Optimism Picnic" organised by the co-founder of the economic campaign group Looking For Growth cannot go ahead in Hyde Park.

The outlook for the event now appears more pessimistic, falling on an afternoon already forecast to be overcast following a morning of intermittent heavy rain.

The intervention from the parks organisation came in response to a post from an X user complaining about the "large and dangerous unofficial event" (post).

The individual wrote: "I was planning a quiet day out at Hyde Park with my two young children and this large and dangerous unofficial event is very concerning.

"Will your usually excellent rangers/police be on patrol to move on such gatherings?"

The official Royal Parks account (replied): "The event organiser has been contacted informing them that no permission has been granted for this event to take place, they make alternative arrangements for their event & cease public advertising that implies it will take place in the Royal Parks."

The Royal Parks account had not posted since April, and the bulk of its recent activity has been in replies to user complaints on the platform.

Supporter Shiv Malik described the park authority's intervention as "another shot in the war on fun."

He added: "Millions of young people say they are lonely. You try and hold an optimist picnic and there's an instant crack-down."

A special picnic blanket had been prepared

Joe Reeve, a co-founder of Looking For Growth and the main organiser of the event, had said in a promotional post on the same platform that more than 1,000 "optimists" were planning to attend.

Looking For Growth is a campaign group that advocates for faster economic growth in Britain, and the picnic was framed by its organisers as part of a broader pushback against what they see as a pessimistic national mood.

Reeve told City AM: "Since sharing my intent to gather optimists for a picnic, I've been blown away by the positive response with over 1k people registering. It turns out that, despite the doom and gloom, there are young Brits out there who believe in Britain's future."

He added: "I've responded to The Royal Parks directly, and am optimistic(!) that we'll be able to find a way to accommodate the young people and families who stand for optimism and positivity."

The Royal Parks told City AM: "Any event organiser wishing to organise a small event within The Royal Parks is required to submit an application six weeks ahead of the event taking place to ensure that every new event application is assessed appropriately and in line with park regulations to protect the space and ensure the safety and enjoyment of all visitors.

"In this case, the organisers did not approach The Royal Parks to apply for an event license and the event was unauthorised."

The Royal Parks is the charity that manages London's eight Royal Parks, including Hyde Park, which host thousands of licensed events each year ranging from concerts to mass-participation sporting fixtures, all subject to the same application process.

The LFG co-founder had commissioned a special "Optimism Picnic Blanket", highlighting aspirational picnic snacks such as Whitstable oysters and Kent strawberries, with the event described as "Britain's largest optimistic picnic of a generation".

The picnic was set to include a sports day and an ultimate frisbee competition, with volunteer provisions for both activities as well as litter picking at the end of the day.

Hyde Park covers 350 acres and is a mile and a half long. As it stands, it is unclear whether or not the event is still going ahead.