There's nothing more dispiriting than waiting for a train and when it finally arrives it is much shorter than usual and overcrowded.

South West Trains have issued an apology and explanation for 'recent short-formations'.

The company said: "Our trains are rigorously inspected for the safety of our passengers and staff.

"If an issue is found which requires urgent attention, we often have no choice but to remove the affected coaches from service to enable any required work to be completed before they can return to operation.

"However, due to the make-up of trains, it is simply not possible to remove only one coach from a train. For example, it means that while work is on-going, a 12-car train may have to run as an 8-car train."

It said it was spending £275m more on 258 more carriages between now and 2018 to increase capacity in peak-times by 30%.

But it admitted it had failed to meet a target of fully refurbiushing its fleet by summer 2014 because of unforseen difficulties.

The company added: "On these occasions we fully understand your frustration at having to board a short-formed train which may be overcrowded. We apologise and assure you that we are working hard to increase capacity as quickly as possible."