An investigation has been launched after porn was played over the speaker system of a South Western Railway train for all to hear.

A video was posted to Twitter on Saturday by Paul Brunton with the caption "my tube driver casually watching porn whilst leaving the tannoy system on."

Passengers can be seen giggling in the background as the audio blares through the carriages

It was later revealed that the train was not a Tube, but instead the 11.32am SWR service from Wandsworth Town to Waterloo.

A spokesman from the rail service said: “South Western Railway has a policy of blocking inappropriate material, including pornographic websites, on its onboard and station Wi-Fi services.

"We are investigating this incident to establish how this material was broadcast on our service.

“The incident is wholly unacceptable and we apologise to customers.”