The mystery behind over large parts of south west Wales has seemingly been solved, bot nobody is taking responsibility for it.
The pulsating glare was reported as being seen between Swansea and Carmarthenshire on Tuesday evening.
Some of the suggestions were that it was a drone, a large aircraft, or a spaceship.
But the overriding suggestion was that it was a New Measurement Train (or a Tamping Train) working on the railway line in the area.
The yellow trains, known as the Flying Banana, are specialised vehicles which operates in the UK to assess the condition of track so that engineers can determine where to work.
The specially converted high speed train is laser guided and emits a huge beam of blue light.
The trains ensure the track is correctly aligned and has a smooth level along the rail and generally operate at night.
Tamping Trains have caused UFO sightings across the country in recent years due to their blue beams of light.
Manchester
In August 2018, Manchester Evening News reported a similar sight, which residents described as a "pulsating purple glare".
At the time, a spokesperson for Network Rail said: “We can confirm this was not an unidentified flying object (UFO). It was rather an identified non-flying object (INFO) - namely a railway ballast tamping machine, which uses lasers.”
Liverpool
In August 2019 Network Rail again confirmed a tamper train was using lasers to to mark out an exclusion zone for the workforce in the area.
Gloucestershire
Last October the same thing happened in Gloucester.
After lots of speculation a Network Rail spokesperson said: “Tampers and stoneblowers are track maintenance machines that make sure the track is correctly aligned and has a smooth level along the rail.
Why the train has a blue beam
Network Rail have previously stated that such vehicles use lasers to mark out an exclusion zone for the workforce.
Meanwhile train driver Phil Sullivan confirmed the light was caused by "monitoring for defects and movement in the railway structure".
He added: "The blue light can detect bridge and tunnel measurements, ensuring there's no movement in gauging."
He said there was a fleet of vehicles working across the country looking for defects in railway lines.
Ghost train
WalesOnline reader Gemma Leanne and her friends said she saw the train passing during a rugby training session with a beam emitting out from the top of it.
Andrea Harries said she saw the strange light at around 6.05pm from her garden in Penllergaer .
She said: "I came out into the garden with the dog and saw a blue, purplish light.
"It was bright but dimming every now and then. It moved over to Pontlliw and then towards Llanelli and then it just went."
However Network Rail and rail infrastructure company Colgas both say there has been no work going on in Wales.
A spokesman for Network Rail said: "We have received a number of calls from the media this morning about a mysterious strange blue/purple glowing over Swansea/West Wales. To confirm, this is not us."
With nobody taking responsibility and no record of a maintenance work being carried out on the railway it seems that the blue light was caused by a ghost train rather than a UFO!
