Great Western Tunnels

One question which two or three of you must have had while reading this website is "Which tunnels out there were longer than Tidenham?"

While doing some research on another topic our information-mining team remembered this question and duly produced this lovely table ranking the 29 Great Western tunnels which were over 1000 yards long based on their length. Once we have pictures of all of them it will turn into a much bigger webpage. Until then...

(The stretch of railway which the tunnel is on is mentioned under "route" with the two notable stations/junctions which the tunnel is between in bold. First rank is the tunnel's position in 1930 and second rank is its current position)

Quick guide to imperial measurements:

 Miles  Kilometres  Yards  Miles  Kilometres  Yards
 1 1.58  1760  0.57  0.9  1000
 ¾  1.19  1320  ½  0.8  880
 0.63  1  1111  ¼  0.4  440

Rank Name Length (yards) Route  Status and Notes  
 1/1 Severn  7669 Swindon - Patchway - Severn Tunnel Junction - Newport Active. Formerly longest railway tunnel in UK. Originally longest tunnel in the world.  
 2/2 Chipping Sodbury  4433 Swindon - Patchway - Newport Active  
 3 Rhondda  3443 Pontypridd - Treherbert - Cymmer - Bridgend Closed. Longest tunnel in South Wales. Sealed and buried at both portals due to internal subsidence.  
 4/3 Box  3212 Swindon - Bath - Bristol Active. Said that sun shines through it on Brunel's birthday.  
 5 Merthyr  2497 Merthyr - Hirwaun Closed. Longest accessible tunnel in South Wales.  
 6/4 Llangyfelfach  1952 Neath - Llanelli Active. Freight only Swansea avoiding line.  
 7/5 Caerphilly  1933 Rhymney - Caerphilly - Cardiff Active  
 8/6 Halton (Sutton)  1922 Chester - Helsby - Warrington Active. Scene of a fatal accident in 1851.  
 9 Wenvoe  1867 Barry - Pontypridd Closed  
 10/7 Sapperton Long  1864 Swindon - Gloucester  Active. Part of the mainline to South Wales until opening of Severn Tunnel.  
 11/8 Patchway New  1762 Newport - Severn Tunnel Junction - Patchway - Swindon Active. Single-line tunnel on double track railway so used only by eastbound trains.  
 12/9 Clifton Down  1751 Bristol - Avonmouth - Severn Beach Active. Nine yards short of a mile. "Down" as in "hill" not " heading away from London".  
 13 Cymmer  1595 Bridgend - Maesteg - Cymmer Closed  
 14/10 Colwall New  1585 Hereford - Ledbury - Malvern - Worcester Active. Replaced inadequate Colwall Old tunnel  
 15 Colwall Old  1567 Hereford - Ledbury - Malvern - Worcester Closed. Undersized and replaced in 1929. Now occupied by a bat colony.  
 16 Pontypridd 1323 Barry - Pontypridd Closed. South portal on grounds of University of Glamorgan Pontypridd.  
 17/11 Ledbury  1318 Hereford - Ledbury - Malvern - Worcester  Active  
 18/12 Patchway Old  1246 Swindon - Patchway - Severn Tunnel Junction - Newport Active. Single-line tunnel on double track railway so used only by westbound trains.  
 19 Ballingham  1206 Hereford - Ross - Gloucester Closed  
 20 Tidenham  1190 Chepstow - Monmouth Out of use. Track in place but tunnel fenced off.   
 21 Pinnock  1173 Lostwitheil - Fowey - Par Out of rail use. Now a lorry road for china clay traffic to Fowey Docks.  
 22/13 Ardley  1147 Banbury - Aynho - Bicester - High Wycombe Active  
 23 Gyfylcha (Tonmawr)  1109 Port Talbot - Tonmawr - Cymmer Closed. Scene of a fatal accident in 1902. North portal collapsed in 1947, closing tunnel.  
 24 Whiteball  1088 Taunton - Tiverton - Exeter Active. Descending to Taunton from this tunnel City of Truro achieved 102.3mph in 1904.  
 25 Bullo (Haie Hill)  1065 Newnham - Cinderford Closed. Longest tunnel in Forest of Dean.  
 26/14 Somerton  1053 Castle Cary - Taunton Active  
 27/15 Dinmore  1051 Hereford - Leominster Active  
 28/16 Bristol No.3  1017 Bristol - Bath - Swindon Active  
 29 Cwmcerwyn  1010 Port Talbot - Maesteg - Pontyrhyll Closed  

Another tunnel of over 1,000 yards for the Great Western network would theroretically bring the total up to 30, if anyone feels like digging one.

The oldest tunnel featured on this list is Bullo, also known as Haie Hill. When opened in 1810 it was the longest railway tunnel in the world - although it was only used by a horse-drawn tramway for the first couple of decades, which meant that the steeply-graded bore didn't have to feature annoying things like ventilation shafts which might have allowed steam locos to work trains through it with any degree of comfort.

The tunnel closed in 1965 after a working life of 155 years - something which several of the active tunnels featured here haven't achieved yet and most of the closed ones never got anywhere near. Both portals are still visible - this is the west one - but have been firmly sealed up with brick walls. There is a certain degree of optimism with the three tunnels on the former Newnham-Cinderford line that they will never need maintenance again.

Now the longest visible tunnel wholly within South Wales, Merthyr - also known as Abernant - Tunnel is unusual for having completely mismatching portals. This is the single-line east portal, from which trains descended over various long-gone junctions to Merthyr Tydfil. The west portal was wide enough for double track, although the tunnel only ever took a single running line.

Abernant is slightly curved at each end, providing a dead straight central mile between the portals which has never seen sunlight, the tunnel having no ventilation shafts. During its career it was mostly noted for an occasional habit of falling in at short notice. It closed in 1964; re-opening to rail transport is unlikely for some reason but, equally curiously, the cycling lobby are starting to show an interest in it. Until then, the wall just inside the portal is graced with a sign explaining that it is a private tunnel with no public right of way.

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