I'm delighted this is happening at last. While the line probably needed economies back in the 60s, I suspect a lot of politics meant it was pruned more severely than was necessary. What it could really do with now along with this loop is an extension of the Tisbury loop to the east, as nearly everything has to stop here. As it's not possible to extend the loop into the station (sold off land), it might be possible to extend it east so this can also be a dynamic loop. Another place which could do with a loop is Crewkerne - the platform's in situ and I read once (not sure if it's true though) that Chard Junc - Yeovil Junc is the 4th longest stretch of 'pure' single line in the country. Given that it's on NR^» (Network Rail - home page) maps as a principal route, that's absolutely ridiculous!

I'd be surprised if building it today wouldn't be more expensive. As bemmy points out you'd have a much more expensive workforce, plus a considerable amount of health and safety regulations - something which didn't overly concern Mr Brunel. Even given the difference in construction techniques and materials, it would surely take longer and probably involve extra staff, so I'd have thought it would definitely cost more today.

On the subject of slack, I used the Brizzle-Paddington line last weekend and the train arrived at Paddington over 5 minutes early, in just 24 minutes from Reading. On the return the train was 10 minutes late leaving Reading due to engine problems and we were informed the train would not exceed 100mph as a result. Even then, it was only 6 minutes late into Bristol. I suspect this might be a result of the fines incurred for late running.

I believe the all-time record between Plymouth and ESD is 46 minutes, achieved by a HST^▸ (High Speed Train). I think that was when speed limits could be interpreted a little more liberally than now, although it's probably still achievable in that time.

As far as I'm aware, there have never been any plans to extend the M5 further south due to the barrier of the Haldons - it would be far too expensive. The same reason that the railway heads south along the Exe.

It's notable as well that Plymouth has a far poorer local service than Exeter. Only 1 line through Exeter closed - the Teign Valley line - and that was pre-Beeching. The lines to Exmouth, Barnstaple, Paignton and Okehampton are still there, while there's plenty of local stations all around Exeter. Plymouth on the other hand has just the Gunnislake branch and some Cornish traffic, plus a few local stations to the west of the main station. But then as an Exeter fan, I think that shows the importance of the Devon capital compared to that other place down the road.

According to the Rail Regulator's Office at http://www.rail-reg.gov.uk/server/show/nav.1529, a grand total of 172 people used Dorchester West on the Weymouth-Bristol line in 2006-07, whilst about 415,000 used Dorchester South on the Weymouth-Waterloo line.

Whenever I've used West station there's always been about 10-20 people getting on or off. I can't help thinking that the numbers may be just a little skewed (I think nearly all tickets are credited to South) . Does anyone know roughly how many people do use West and South stations in an average year? I'm just curious as it wouldn't entirely surprise me if the DfT^» (Department for Transport - about) decided to use the 172 as an accurate figure in the future. London is such a long way from Dorchester after all... 

Sorry, yes I meant in practice. What I was trying to say is that it's more likely that anyone not abiding to the terms of use of a Megatrain fare would have a higher likelihood of being caught out than an advance fare.

That said, I obviously don't condone ticket fraud in anyway. If you want the advantages of an advance fare, you have to accept the lack of flexibility and abide by the terms. If you deliberately choose not to, you can't complain if you're caught out.

I've never actually used one but I believe they're (not surprisingly) very inflexible. Unlike some tickets you can't get off short of the destination e.g. Clapham Junction, otherwise you'll be treated as not having a valid ticket. You obviously can't break your journey either. While in theory you could get off at an unbarried station I think the staff at the barriers have a list of booking references, so if they don't tick yours off it could lead to problems.

It sounds as though you're best sticking to advance purchase tickets - they seem to be easier to buy on SWT^▸ (South West Trains) routes into London than FGW^▸ (First Great Western) routes in my experience.

There used to be a very bumpy bit of track between Topsham and the M5 bridge on the Exmouth branch. Lurching over it on a 158 was bad enough: I shudder to think what it was like on a Pacer. I think it's been replaced now. Another bouncy bit that may still be there is on the up line i.e. Exeter-bound, just west of Teignmouth. I think it's on the crossover line used when the down line on the sea wall is out of bounds - you'll know when you pass over it!

I think the fast lines in the middle are 100mph from Worting Junction to Wimbledon with 90mph on the outer slow lines. I'd assume that the electric Desiros on fast Bournemouth services can still reach and maintain 100mph without difficulty. The Surbiton/Wimbledon area is where things start to get really busy. I don't often travel in that area though, so I could be wrong.

The line between Salisbury and Exeter has a general limit of 85mph with few restrictions (90mph Salisbury-Worting Junction and 100mph onto London). This is largely because it was built as a main line to rival the Paddington route, so it's fairly straight and none of the gradients are steeper than 1 in 80. The Weymouth - Castle Cary route was also built as a main line (Weymouth-Westbury-Swindon-Paddington) and so that's also fairly straight. That's presumably maintained to a lower standard as the general limit between Dorchester and Castle Cary is 75mph, although it's 40mph between Yeovil Pen Mill and Yetminster, while there's a 15mph through the passing loops at Dorchester, Maiden Newton and Yeovil.

I don't work for the railways BTW^▸ (by the way) - I just like to know how fast I'm going as a passenger!