[Excerpt from “Green and Pleasant” Sidebotham 2018]
The third bridge is the “Iron Bridge” over the Swilgate. It never appears to have been given any other name, and its history is obscure. It must always have been a foot bridge, because of the comparative narrowness of the bridge, and it may be “about 1850”, as suggested by Verey. (Buildings of England Gloucestershire: The Vale and Forest of Dean) ed. Verey) in the Pevsner series.
It depends on what you consider is “about”!
1 Orientation If the bridge were to be routed from the town, via an alley to Perry Hill, there would be no need to site the bridge at an angle. There are several sites where the bridge could be positioned north-south rather than north east-south west which is its current orientation. This suggests a path straight from the end of Orchard Court or one of the alleys, to Lower Lode Lane, across what is now the cricket field, to the junction of the old main road to Gloucester, and also the Gupshill Road, the route to the relatively new town of Cheltenham via Tredington or Combe Hill. Why was it built? Now it serves as a way of reaching a Housing Development (Priors Park, 1946), but in 1850 there were no houses there, and so it is more likely to be heading towards Lower Lode.
2 Method of Construction Secondly, its construction is primitive. It is almost as though the builders weren’t aware of the properties of iron and built it like a stone or brick bridge. (The very first Iron Bridge, built by Abram Darby in Coalbrookdale, which was opened in 1781, was constructed using methods used in wooden bridges).
3 Primitive Design Thirdly, it consists of two very short primitive spans and it is reminiscent of any clapper bridge found in the West Country, where there are short spans because of the lack of strength of the stone walkways. Clapper bridges are ancient, and like this iron bridge, the spans are not archlike.
4 Elliptical Arches in Abutments The fourth item of interest are the abutments with their elliptical brick arches. They are brick and not iron, and they are elliptical and not circular. I.K. Brunel built a large elliptical arch in brick over the Thames at Maidenhead in the mid-1830s. He was probably familiar with small elliptical arches like these, where there was a small load, because although there would be a slight increase in sideways thrust compared with a semi-circular arch, it would not be significant, and the arch would have fewer bricks in it. The central pier with its cutwater probably causes more sideways thrust on the bridge through water resistance from debris, than it would receive from water currents.
5 Fixing of Railings/Parapets
Also, the iron parapets/railings are joined to the decks by reinforcing scrollwork in common use from about 1780 to 1810, as railings and balconies in the new town of Cheltenham. The ends of the hand rails have been shaped.
6 Previous Comments
This might suggest the work of a skilled blacksmith at the end of the reign of King George III, maybe working to crude drawings not prepared by an engineer. It is as though the person responsible for this structure had never seen an iron arched bridge, which would mean that its date of construction would predate that of the Quay Bridge by several years.
The bridge walkway is made of four sections. Only the inner two are made of wrought iron plate. The outer two sections taper inwards to the narrower iron sections, as though the designer were a little suspicious about the new material., or else there wasn’t much of the “new” material available
And finally, why is it such a substantial structure, when a simpler form would have sufficed? Why is it not made from wood or stone unless it were important? Did the Iron Bridge have an importance which has been lost in the last two centuries?
My opinion maybe incorrect, but speaking as a Chartered Materials Engineer, I would estimate the date of the bridge to be not Verey’s “about 1850” (however he came to that year), but about 1800 to 1810, at the latest, which, if accurate, would make it a very early iron bridge indeed, and almost half a generation older than the Quay Bridge and the Mythe
Bridge of the 1820s. My deductions are necessarily subject to confirmation by someone on the spot, because I am hypothesising using photographs only
7 Dating of Bridge Since I wrote the above, I have come across a map of 1811 in the British Library, and the bridge is marked on it. This makes the Swilgate Iron Bridge Tewkesbury’s oldest iron bridge by at least eleven years and it is well into its third century!
8 Reason for just calling it the Iron Bridge Might the simple fact that it was, and always has been called just “The Iron Bridge” suggests that it was the iron that somehow made it different from all other bridges in the area. That it was the very first bridge made of iron anywhere in the vicinity. There are comparatively few river crossings in North Gloucestershire. There were no railways at that time. Canals had brick bridges so might it be the oldest iron bridge in the Three Counties? Might it be dated back to the end of the Eighteenth Century?
Comments would be welcome please so that they may be incorporated into my booklet “Green and Pleasant” soon to be available in .pdf form free of charge (voluntary donation to THS) from sidebothamjohnATgmail.com (change AT for @)
POSTSCRIPT
As Kevin Cromwell has stated elsewhere, the Iron Bridge is a listed structure. However, listed structures have been known to be accidentally damaged and/or destroyed. I do not know how many times this bridge has been repaired/refurbished, and having seen it again since I wrote the above, it might just possibly be of a slightly later date than I first thought. I still think it is earlier than 1850, but probably later than my first estimate of 1810 (the bridge on the 1811 map might have been wooden, for instance). But it IS early, and probably much the same age as the Quay Bridge (1822). Tewkesbury is certainly lucky to have it, but two things are important:
1) The bridge must be refurbished/rebuilt/repaired with PROFESSIONAL archaeological advice
2) The bridge should be signposted down one or more of the alleys from Barton Street, and "Out of the Hat" given information for tourists.
ALSO There is the remains of a hinge at the end of the bridge. What was it for, and why is it there?
