A Bristol father who threw his two children off a hotel balcony, killing his son, is launching a High Court challenge today against an inquest verdict.

John Hogan is seeking to overturn Avon coroner Paul Forrest's ruling earlier this year that six-year-old Liam was "unlawfully killed".

Former tiler Hogan, 34, of Bradley Stoke, pushed Liam and his two-year-old sister, Mia, before jumping himself following a row with his then wife, Natasha.

Liam died, but Mia survived the 50ft plunge from the fourth-floor balcony whilst on holiday in Crete two years ago.

The unlawful killing verdict led to a police inquiry that could open up the possibility of a new murder trial in Britain.

But Hogan, acting through his sister, is seeking to have the verdict quashed. Lawyers are expected to argue that it was an irrational decision based on insufficient evidence.

Hogan was cleared of murder by a Greek court in January, when a jury decided he had been suffering from "an earthquake of insanity".

He is currently being detained in a secure psychiatric unit in Greece, but it is believed he could be released in the near future.

In March this year an inquest into Liam's death was told that the Greek trial had ignored evidence from key witnesses. Mr Forrest arrived at his verdict after taking this new evidence into account.

Today lawyers instructed by his older sister, Christine O'Connor, from St George, will seek permission to apply for judicial review.

They will ask Lord Justice Dyson and Mr Justice Griffith Williams, sitting at London's High Court, to rule it is arguable that the coroner went wrong in law and applied the wrong legal test.

Hogan's former wife, Natasha Visser, who has married again, is represented at today's hearing as an "interested party".

The row that preceded Liam's death came at a time when her marriage to Hogan was under stress.