Do you know what a veteran tree is? It’s not as straightforward as you might imagine.

Some trees get veteran status because of their history - so far so expected - but others become officially designated veterans because of their arboricultural or ecological importance.

Most veterans on the Heath fall into that category because of their age or the biodiverse habitats they are a key part of.

This weekend is the perfect time to learn more. As part of the 2019 London Urban Tree festival, the City of London Corporation and the Ancient Tree Forum (ATF) have joined forces to give the public an insight into what makes some of the Heath's trees very special indeed and on Sunday are holding a guided walk around a few of the most fascinating.

Then on Wednesday the two groups will officially launch the Heath's "veteran tree trail between 10am and 2pm.

Jim Mulholland from the ATF told this newspaper: "Working with the City of London we have developed some fascinating guided trails on the Heath.

"Although they're aimed at tree conservation professionals, we wanted to highlight to the public the veteran trees."

Jim explained the ecological category of veteran trees is perhaps the least understood.

He said: "People think of decay as a bad thing but decaying trees are particularly good for fungi and invertebrates.

"And then the decay in an old tree can often provide an environment that's only possible there. The only way of protecting that is to keep the trees alive, and prepare new trees to become veterans afterwards."

The most famous Heath veteran is probably the Bandstand Oak but Jim added that the walk, also being led by the City of London's tree conservation expert David Humpreys, would go in some surprising directions.

He said: "There are some interesting areas down by the newly-landscaped ponds, in particular."

Jim also praised the "absolutely remarkable" work being done by the City of London to conserve their veteran trees.

Both the guided veteran tree walk - meet at 10 on Sunday at Golders Hill Park - and the launch event on the Heath on Wednesday are free but require advance booking. See eventbrite.co.uk/e/veteran-trees-of-hampstead-heath-tickets-61577414705 and visit ancienttreeforum.co.uk