Many commuters are used to everyday objects causing immense disruption to their train journeys, including leaves on the line and coats trapped in doors.

However, Network Rail has warned of a mounting hazard, that costs more than £1m a year to fix and causes hours of delays - helium balloons.

The publicly-owned company, which is responsible for Britain's rail infrastructure, recorded 619 balloon-related incidents across Britain in the past 12 months.

Network Rail has warned commuters not to take their celebration balloons onto train platforms as they become entangled in overhead wires and cause delays, and even death.

Many of the episodes include balloons getting tangled around high-voltage overhead wires, causing delays as the electricity supply must be turned off while they are removed.

James Dean, chief operating officer for Network Rail's London North Western route, said: "If you're on a railway station platform with a foil balloon filled with helium on a string and it comes in contact with the overhead wires carrying 25,000 volts, that could cause huge injury or death.

"Ideally, we'd ask people not to bring balloons into our stations at all.

"Alternatively, carry them in bags so the risk of them floating upwards is minimised."