What is the most serious crime in England?

Answer 1

Since the theoretical mandatory death penalty was abolished for treason and piracy in 1998, then murder is arguably the most serious crime in English law since it has the highest penalty, i.e. a mandatory life sentence (usually with the possibility of parole though).

In contrast, all other comparable serious crimes (including treason), only have a maximum life sentence - it is not mandatory. However, unless I am mistaken, there is still a law that bars bail to those charged with treason, whilst those charged with murder could get bail (though that's rare). Also, it's a crime not to report to the authorities an act of treason or terrorist offences, but there's no offence relating to not reporting (non-political) murders.