Taking Stock
Church and Street

A Low Point for the Canal

_IMG2824The towpath hangs out over the edge of the aqueduct.

The Iron Trunk, the aqueduct that carries the Grand Union Canal 40 feet above the Great Ouse, is the third one to be built here.

The first one collapsed, the second one was temporary, and the one we have now is 210 years old. The canal company changed the course of the river and the shape of Buckinghamshire to build it.

Here’s the timeline.

In July, a meeting is held in the Bull Hotel in Stony Stratford to attract subscribers to the planned Grand Junction Canal. So many people turned up that the meeting had to be moved across the High Street to the church. But it was still a crowded meeting.

The canal (now part of the Grand Union Canal) would run from the Oxford Canal at Braunston in Northants, to Brentford. on the Thames in London. It would be nearly 93 miles long with around 100 locks.

The company were asking for £350,000. Before 9pm that evening subscribers had promised a total of £361,001; the meeting was a success.

The Ouse Valley before the canal 1000pxBefore the canal came, there were just fields here. The county and parish boundary ran along the North bank of the river, until it turned to follow the course of the River Tove. There may have been more hedges than I’ve shown here, but any trace of them is now under the embankment.

The original plan was for the canal to cross the Great Ouse at river level. this wasn’t great for several reasons:

There would be a time consuming flight of four locks on each side of the valley to make the change in levels; around 40 feet down and back.

The crossing would be the lowest point in over 50 miles of canal, and much canal water would be lost into the river.

It would be hard if not impossible to take a boat across when the river flooded.

Instead, an aqueduct and embankments are proposed. A temporary canal with two flights of four locks is built and opens that September, to one side of the proposed embankment.

The Wolverton end of this stretch started at the angled wall of the present day wharf. The Cosgrove end joined the existing canal at the winding hole just this side of Cosgrove lock.

Cosgrove's first aqueduct 1000pxThe first aqueduct was built on dry land and the river diverted later. There’s a temporary gap in the embankment for the river. I think the river would have been widened where the temporary canal crossed it, so the river water slowed and did not push the boats sideways so hard.

But I think the boats would still have needed help crossing. Boats heading South East would need pulling against the cross flow, from the narrow island between the canal and river, so I’ve shown a bridge to that island. Boats heading the other way could be pulled from by the lock on the North West side of the crossing.

In August, work begins on the embankment and the first aqueduct. It would have three arches of brick and stone, with a wooden trunk lined with clay. It is built on dry land, and the river will be diverted through it later.

The river is now fully diverted. The aqueduct opens to traffic on the 25th of August. It is said that its arches were already sinking.

The county boundaries follow the North bank of the river. Now the river has been straightened to run through the aqueduct, the boundary will be changed to follow the new course.

A small part of Buckinghamshire is lost to Northamptonshire, which also means that same bit of land changes hands from Wolverton parish to Cosgrove parish.

In January, part of the embankment near Cosgrove collapses. It is repaired, and the contractor is blamed. At about the same time a permanent leak is found in the aqueduct.

In February the aqueduct collapses. The lock keeper at Cosgrove is first to notice the disaster, at 11 pm. He closes his lock gates and sends out the alarm.

Two of the three arches have collapsed. Enough water is able to pass through the more or less intact Northern arch (which had been shored up with timber shortly after the aqueduct opened) to prevent the Ouse backing up and flooding Stony Stratford.

The contractor is again blamed after an investigation, and later loses the matter in court.

The temporary canal is reopened.

A temporary wooden trunk aqueduct is constructed, and finished in June.

The Ouse Valley and the Grand Union Canal today 1000pxThe valley as it is today. There are remnants of the temporary canal in the form of ponds and wet land, and hollows in the woods. There are some old lock gates on the site of one of the old locks, next to the path.

The path along the bank goes under the canal through a tunnel; a cow creep. The path joins up with the towpath. The county and parish border was changed to follow the new course of the river some time in the 18th Century; Bucks and Wolverton have lost some land.

_IMG2856The central stone pier, and behind, one of the brick faced abutments.

The Iron Trunk aqueduct opens on the 21st of January. It is made of cast iron sections from the Ketley Iron Works in Shropshire, sent down by canal and assembled on site.

The stone abutments on each side of the river are rebuilt and refaced with brick. The job won’t be completed until 1921.

The aqueduct is drained for maintenance for the first time.

The Iron Trunk aqueduct is repainted.

The Iron Trunk is drained for maintenance, for only the second time.

The aqueduct, now 200 years old, is repainted in the original colours of grey, white, and red. It took 700 litres of paint.

Over two centuries since it first opened, the Iron Trunk aqueduct is still in use every day. There are remnants of the temporary canal still left on the Buckinghamshire side of the river, and some ponds and wet ground across the river where that canal once ran.

I used Pentax zoom lenses for the photos in this post; earlier versions of the 10-17mm fisheye and the 16-50mm lens, but the same model of 60-250mm lens as in the link.

I make a small percentage from sales through these links, no matter what you buy while you are there on Amazon. This helps me but costs you nothing, so if you make a purchase via the NBW, thank you.

If you have any comments or questions about this post, please leave a comment below.
If you liked this post and want to find out more about the North Bucks area, please


Feed You can follow this conversation by subscribing to the comment feed for this post.

There is a discussion in a thread on youtube about the locks on the temporary canal. Why are they modern looking iron construction?

You are right, they are of modern construction. I found the video you mentioned and I think these steel balance beams were fixed to the remains of the original lock gates, just to give the general (non-boating) public a better idea of what they were looking at.

I think this reconstruction was done in about 2007-2008 for the Ouse Valley Park; I have photos from 2009 that show it all in good condition, but the landscaping has been done long enough to lose that just-finished rawness.

They are not even real balance beams; too lightly built to balance the weight of a lock gate. The first one we see also has cross bracing too flimsy to last long on a working lock. In short, they are a well intentioned fake. I'll have to go up and have another look.

In the planning stage they considered reusing these temporary lock gates in the Stoke Bruerne flight, but I don't think that ever happened.


PS, here's a link to the video:`

Verify your Comment

Previewing your Comment

This is only a preview. Your comment has not yet been posted.

Your comment could not be posted. Error type:
Your comment has been saved. Comments are moderated and will not appear until approved by the author. Post another comment

The letters and numbers you entered did not match the image. Please try again.

As a final step before posting your comment, enter the letters and numbers you see in the image below. This prevents automated programs from posting comments.

Having trouble reading this image? View an alternate.


Post a comment

Comments are moderated, and will not appear until the author has approved them.

Your Information

(Name and email address are required. Email address will not be displayed with the comment.)