Virgin Trains has announced it will spend £3.5m on refurbishing its entire fleet of trains to remove the bad smell coming from its toilets.
The odour, which has led to passenger complaints to the company, comments on social media and to newspapers, has been dubbed the "Pendolino pong", which pervades large sections of the trains.
All of the 56 electric Pendolino trains and 21 diesel-powered Voyagers need to be treated.
A Virgin spokesperson told the Sunday Times: "Although toilet smells on our trains have attracted comment over the years, it's worth setting that in context.
"The most recent National Passenger Survey showed satisfaction with our on-board toilet facilities significantly higher, 60 per cent, than the average for long-distance operators, 52 per cent."
According to the Independent, the smell is believed to come from the air conditioning inlets placed too close to the toilets, which are spreading foul-smelling air throughout the trains.
In 2007, Virgin Trains tackled another problem with its toilets when passengers were unable to use them due to their futuristic style and panel of buttons.
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