BBC Four, No Go Britain
A glint of street light on sharpened steel is a hint that there could soon be trouble in the far corner among the trees.
Armed gangs have made parts of the UK no go areas
About 40 teenagers have gathered on their side of a thin strip of grass that separates their estate from their sworn enemies - their nearest neighbours.
Every one of them is armed. They wave their weapons high above their heads, the weapon of choice seems to be a golf club.
But some of these kids are carrying broken bottles, iron bars, heavy oak bedposts and, though I find it hard to believe my eyes, the odd sword.
'Call to arms'
This piece of grass is, effectively, the "no man's land" between two competing gangs, or "teams" as they like to call themselves, in the east end of Glasgow.
The team from Garthamlock wolf whistle.
These whistles are a recognised signal, a call to arms, and are meant to antagonise the enemy from Ruchazie, gathered opposite by a road that dissects the two housing schemes.
Soon, the Garthamlock team run down the hill and onto the turf, the Ruchazie team cross their road and run towards them.
They meet. Blows land. The fight begins.
It happens every weekend. Kids get hurt. And nobody, it seems, is able to stop it.
In fact, adult voices from a balcony on the Ruchazie side scream advice and encourage their "team" on to victory.
I went back the next night to find out why they fight.
"Something to do," said one of the battle-scarred fighters.
"We've always done it, our parents did it," said another.
This was just one of a number of shocking events I witnessed living in two of the UK's most deprived areas for a BBC Four and Six O'Clock News investigation called No Go Britain.
Tower Hamlets lies side by side with City of London wealth
I'd read the term "no-go zone" many, many times but wanted to know what it really meant, and whether they truly existed.
I now believe they do. And they are a shocking indictment on our society.
But my first stop wasn't Glasgow, it was Tower Hamlets, "Britain's most deprived borough", which lies between the glittering twin pillars of Docklands and the City of London.
I rented a flat for almost a month. The borough is probably most famous for Brick Lane - home to dozens of Indian restaurants and artists such as Tracey Emin.
One of the country's most famous modern landmarks, the Swiss Re Tower - better known as the "Gherkin" - sits virtually next door to one of its most rundown buildings.
The "heroin high rise" that is Denning Point tower is 23 floors of poverty and misery.
The stairwells are ruled by heroin users and prostitutes - keeping the locals locked behind heavy doors.
Denning Point's stairwells are used by addicts and prostitutes
About a third of the people living here are of Bangladeshi origin - this rises to almost 50% among under 16s.
Teenage gangs and crime are a big problem here. But it is not a race issue - Asian on Asian attacks are the norm.
I'd seen many, many gangs of teenagers gathered in the tough Tower Hamlets estates, some selling drugs or up to mischief.
Others lighting fires. Some simply hanging around.
But I was surprised by the early evening attack on me, when it came - because it was from around a dozen 14-year-old boys in one of the borough's biggest open spaces, Victoria Park.
A boy, his face covered in a bandana, threatened to slash my face with a home made knife - just for looking at him.
'Finger in the dam'
I met some wonderful people who live in Tower Hamlets and the east end of Glasgow with horrific tales to tell.
And there are many good people trying to do the best they can to try and help the situation.
But there is a depressing "finger in the dam" feel to what's being done.
My journey is over. But those who remain have adapted to the fear, grown used to the violence.
They've done what we'd all do - bolted the door and stayed away from the places where they know danger lies.
The Metropolitan Police said "considerable resources" had been put into policing Tower Hamlets and that street crime and other offences had been "significantly reduced" in the past three years, including a 25% drop in violent crime in the past 12 months.
In a statement, the force said it had also introduced a Safer Neighbourhoods Team in the Whitechapel area dedicated to tackling anti-social behaviour that made people feel unsafe.