"He is now in custody, being questioned on suspicion of murder. Just suspicion."
According to The Times earlier today, the man "has been arrested on suspicion of murder"
In the UK, police arrest people on the suspicion that they have committed an offence.
It is not the police, nor the CPS, who decide that a person is guilty of a crime. It is either a magistrate, judge or jury that decides this.
Everyone who is arrested by the police (unless there is a warrant out for their arrest) is arrested on suspicion of having committed an offence - unless the offence was actually observed taking place.
If I may point you to the Police and Criminal Evidence Act 1984, Section 24(2)
24(2) If a constable has reasonable grounds for suspecting that an offence has been committed, he may arrest without a warrant anyone whom he has reasonable grounds to suspect of being guilty of it.
The language of the law is all about "suspicion". It is only when a court gives its verdict (ie guilty or not guilty), or a person admits the offence, that a person is then convicted of that crime.
Up until then, everyone is indeed innocent until proved guilty.
But to try and say that the police have arrested him "on suspicion" and so that means nothing doesn't really fly.
Yes, he may indeed be entirely innocent. They may have the wrong person; it may not be murder but it may be manslaughter etc.
But I would suggest that it would be rather unusual for the police to arrest somebody for murder when there is not evidence to suggest that a murder has taken place.