The ceremony will begin at 3.30pm just behind the Thames Barrier. Guests will be invited to walk east along the line of path down Bowater Road for an opening ceremony at the bottom of the raised walkway in Warspite Road.
The route should be available for public use from about 4.30pm.
The link joins the Barrier to downstream King Henry’s Wharf.
It also means that the Thames Path national trail to the source in Gloucestershire from the Barrier now joins seamlessly with the unofficial extension which runs continuously from the River Darent confluence near Erith.
From Wednesday we can say that the Thames Path starts not at Charlton but at Slade Green Station.
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This is the first summer when walkers can enjoy the riverside path at Inglesham in Wiltshire.
Some people could be setting out on the Thames Path unaware that there is a great improvement upstream of Lechlade.
Inglesham has long been the place where the river changes dramatically. Navigation ends and with it the towpath.
With no towpath walkers continuing to Cricklade and the source have always had to take to the road which during 20th century became unpleasant and even dangerous.
But since last October this main road ceased to be part of the Thames Path. Walkers can now stay by the river for a further 1.75 miles beyond Inglesham church.
This is the stretch of river which poet Percy Shelley tried and failed to see in 1815.
Inglesham church, saved from restoration and Victorian ‘improvement’ by William Morris, is a delight to visit. At present it is closed during restoration of wall paintings but it is worth trying the door later in the summer.
Opposite the little church is a set back kissing gate leading to a grass path. Follow this way down to gates at a field and bear right to reach the river.
Stay by the winding river as a footbridge carries the path over a branch of the River Cole as it enters the Thames.
Later the way is fenced on the inland side and there are several gates. After passing through a wood, the path turns sharply to the right to cross high over an inlet.
Here there is a surprise view directly along a grass airfield runway. Stay on the fenced path between the airfield (left) and the river.
At a stream, the Bydemill Brook, the path turns inland to cross at a gated footbridge before continuing inland on the far side.
Beyond a gate there is a T-junction by a footpath ford (left). This was the old approach for those who in the past had walked along the main road.
Ignore the ford and turn right to another gate and bear left to a join a path. Do not cross a footbridge (left) but go right along a wide enclosed path.
This is the existing Thames Path which regains the water higher up.
The unofficial Thames Path extension from Erith allows many to begin their long walk where there is a feel of the estuary.
But this recent addition does not join the national trail’s start at the Thames Barrier. There is a rather unpleasant detour away from the river between Woolwich’s King Henry’s Wharf and the Thames Barrier garden.
This involves walking along Woolwich Road which has very heavy traffic.
The only bonus is a McDonald’s by a bus stop.
But this week contractors are due to hand over to Greenwich Council a riverside route. The ‘missing link’ as it is called locally will be filled.
Some minor highway resurfacing has yet to be undertaken and new signposting is not ready.
But it looks as if the promised ‘late spring opening’ will be achieved.
It will be possible to walk the length of King Henry’s Wharf and go up on to a raised walkway. This curves round into Warspite Road. The at present gated Bowater Road, which runs parallel to the river, will then take the Thames Path to the Thames Barrier.
It will come as a surprise to many that the Thames Path is about to be extended thanks to the England Coast Path.
There is already an unofficial start to the Thames Path at Erith which is eight miles downstream from the official start at the Thames Barrier.
Soon it will be possible to start at Grain on the so-called Isle of Grain in Kent.
This continuous extra 42 miles is expected to open in 2020.
The distance from the Thames Barrier to the river’s source at Kemble in Gloucestershire is 180 miles.
The distance from Grain in Kent to the source at Kemble will be 230 miles.
The Thames Estuary Partnership is encouraging walkers to let Natural England know if you think that this new stretch in Kent should also be called and signed ‘Thames Path’ or maybe ‘Thames Path and England Coast Path’.
Views should be sent to SouthEastCoastalAccess@naturalengland.org.uk by Easter.