A teenager murdered his stepmother with a samurai sword and an axe after becoming "deadened" by online beheading videos, a court heard.

Rueben Brathwaite, 17, developed an interest in "murder, death and mutilation" while looking at American website 4chan before he launched his attack on Fiona Scourfield, 54, a charity worker, Swansea Crown Court was told.

On the day of the killing in March, Brathwaite had a cup of tea with his stepmother after a "normal day at school", then lured her outside their home on a farm in Carmarthenshire by saying that her cat had been injured. He attacked Scourfield, causing "catastrophic blood loss".

Brathwaite then called 999 and said he had hit his stepmother with the blunt side of an axe and used the samurai sword to slash her throat.

Prosecutor John Hipkin said the teenager told the call handler: "There's no sign of life. I hit her eight or nine times in the head with an axe.