1978 and BR are hardly relevant to the railway in 2015, where DfT basically mandate x number of carriages and no more. Nothing any operator can do when they are starting with insufficient carriages, even before losing them to the vagaries of failures and maintenance.
I disagree. I think one of today's London and SE operators could feasibly mount an operation like the Blackbushe concert specials for a similar massive event today, as long as it occurred outside peak commuting hours.
Smaller cities can have problems today if a particular event exceeds their normal peak commuter demand possibly (as it seems with the Bristol case) by orders of magnitude.
Bristol has only a very tiny local suburban operation today with historically only very modest passenger demand. The system is soon to be expanded thankfully with more trains and a new line to Portishead, but currently there simply is not a critical mass of sufficient stock and crew based locally to handle such irregular peaks in demand, even if it was worth it commercially for a TOC to do so voluntarily.
Nearby Cardiff has fewer problems dealing with crowds at the Millenium stadium because they do have a comprehensive local suburban network with significant resources. Just like London and the south east, as long as the big match or other event doesn't happen at peak commuter hours, normal off-peak trains can be strengthened suitably and additional trains run to handle the crowds. It's still a squeeze but it works - just.
In days of yore, railway companies used to hang on to some old rolling stock for such contingencies. Clearly they weren't always kept in the best decorative order, but strings of old coaches could be dusted off and pressed into service for 'race week' specials or the summer factory holiday excursions to Blackpool. Road coach companies do much the same today, although it's usually specialist small operators who buy up and continue to run the old vehicles for very price conscious niche markets such as football trips and school contracts.
Perhaps this is a potential use for non-RVAR-modified pacers. Once St Philips Marsh loses its HSTs, fill some of that siding space with old pacers. Use them only as strengthening vehicles to cover peak demand. They would only ever work in multiple with RVAR compliant units, never on their own, so each train would always include at least some compliant accommodation. Would that be legal?
(much to their annoyance) The safety systems are backed up with rules and regs so you are protected by a human as well. 
Earlier reports say about 15-20 minutes, while later on it is implied that it was similar to various incidents where passengers were stuck for several hours? :roll:
