If Keith Schembri, the Prime Minister’s right-hand man until a few days ago, was not on the police radar in their investigations into the murder of Daphne Caruana Galizia, he certainly should have been hauled in for serious questioning by now.

Yorgen Fenech, who is accused of being an accomplice and financing the murder, named Mr Schembri as being behind the assassination and also linked him to a major deal in which corruption is suspected.

Middleman Melvin Theuma pointed his finger at both Mr Fenech and Mr Schembri and claimed they were planning to get rid of him too. He was granted a presidential pardon, indicating what he said has or can be corroborated.

A similar request by Mr Fenech was turned down by the government.

The allegations led to Mr Schembri’s resignation and arrest. The police had said they interrogated “further people in the Caruana Galizia murder case” but mentioned no names. Three days later, they said that, at this stage, they saw no need to detain Mr Schembri under arrest any longer. They did not refer to any investigation into potential obstruction of justice or a major deal involving possible corruption.

That same day, fears were expressed during a late-night Cabinet meeting Mr Schembri and Mr Fenech had plotted to “frame” Economy Minister Chris Cardona for the murder. Some ministers thought the police treated Mr Schembri with kid gloves.

There had been reports of Mr Fenech calling Mr Schembri just before he was suspected of trying to flee. Also, a doctor served as go-between for Mr Fenech and Mr Schembri, even when the former was under arrest.

. It was Dr Muscat’s duty to know what his closest aide, who had access to very sensitive information, was up to. If there is somebody who could have smelt a rat, it was Dr Muscat.

There is compelling circumstantial evidence that the two knew each other well and that their relationship may not have been only business-oriented. That may not be enough to prove a case beyond reasonable doubt in court but it certainly justifies a thorough police investigation.

Joseph Muscat and Mr Schembri are close friends. It was Dr Muscat’s duty to know what his closest aide, who had access to very sensitive information, was up to. If there is somebody who could have smelt a rat, it was Dr Muscat.

That is why the police should immediately investigate Mr Schembri and speak to the Prime Minister. But it is unlikely the Police Commissioner or the Attorney General would act. The Mallia public inquiry can make up for that failure. It is empowered to determine whether any wrongful action or omission by, or within, any State entity facilitated the assassination or failed to prevent it. “In particular whether (a) any State entity knew or ought to have known of, or caused, a real and immediate risk to Daphne Caruana Galizia’s life including from the criminal acts of a third party and (b) failed to take measures within the scope of its powers which, judged reasonably, it might have been expected to take in order to avoid that risk”.

As Times of Malta argued editorially a few weeks after Ms Caruana Galizia’s murder, the President too has a role to play as the guardian of the Constitution.

President George Vella ought to summon certain people, including the Chief Justice, the Attorney General, the Police Commissioner and the head of the Security Service, and insist that Malta expects every man to fulfil his duty.