FEW downfalls have been as dramatic and sudden as Derek Mackay’s.

It has now been more than a month since the former finance secretary – once tipped as a possible successor to Nicola Sturgeon – was last seen in public.

He resigned on the evening of February 5 after it emerged he had bombarded a 16-year-old boy with online messages.

The former minister called the teenager “cute”, invited him to dinner and asked that their conversations be kept secret.

Since the scandal broke, Mr Mackay has not set foot in Holyrood, or attended constituency surgeries.

It’s not clear where he is or what his plans are.

The SNP — from which he is suspended pending an investigation — says he is “receiving appropriate medical treatment” adding: “Any decision on his future is for him to make when he is well enough to do so.”

A spokesman for Nicola Sturgeon said there has been no contact between Mr Mackay and anyone in the Scottish Government.

Meanwhile, the Scottish Parliament said it would “not comment upon or confirm whether any discussions have taken place about the member’s return to Holyrood”.

Earlier this week, there were reports senior SNP figures are discussing the possibility of Mr Mackay retiring due to “ill health”. This could see him entitled to a £50,000 payout if he is certified as ill.

A party source stressed his future is “literally nobody else’s decision but his now, at this point”.

Mr Mackay has watched his career publicly implode. It’s natural to feel sympathy for someone in that situation, regardless of wrongdoing. It’s important he receives any help he needs.

But the whole sorry saga also throws up legitimate questions, both about his future and Holyrood’s wider rules.

Mr Mackay is paid £63,579 a year to represent his constituents. They are currently completely in the dark regarding his future and whereabouts.

It seems extremely unlikely he will return to Holyrood.

But under the Scottish Parliament’s current rules, this bizarre limbo could continue right up to the next election in May 2021.

In theory, Mr Mackay could cling on as the MSP for Renfrewshire North and West without ever again setting foot in Holyrood, because there is no mechanism to remove him.

He would continue to be paid a full salary and would also be entitled to around £50,000 as a “resettlement grant” come May 2021 following his 10 years as an MSP.

In the coming weeks he will automatically qualify for a £12,000 severance payment for no longer being a minister. Added up, this is a considerable sum of money.

In Mr Mackay’s old job as a Renfrewshire councillor, this scenario wouldn’t be allowed to happen.

The Local Government (Scotland) Act states that “if a member of a local authority fails throughout a period of six consecutive months to attend any meeting of the authority, he shall, unless the failure was due to some reason approved by the authority, cease to be a member of the authority”.

Legislation introduced to Westminster in 2015, in the aftermath of the expenses scandal, set out a process to remove MPs. This sees a recall petition triggered under certain circumstances, such as a suspension being imposed by the standards committee. If at least 10 per cent of the electorate in the constituency sign it, a by-election is called.

Holyrood has no equivalent of this. The law states that any elected member jailed for more than one year will be disqualified, but that’s about it.

Scottish Liberal Democrat leader Willie Rennie has long advocated a system of recall north of the Border.

This should not be a free-for-all, he insists, and a number of thresholds would require to be met.

The different electoral system in the Scottish Parliament, with its regional lists, would also need to be taken into account.

Speaking at Holyrood’s Standards, Procedures and Public Appointments Committee in 2018, Mr Rennie said: “There have been a number of individual cases in the Parliament — which I will not mention — that go back a number of years, and we have felt helpless to do anything about them, so I would support the introduction of a system of recall here. We need to look at the Westminster system and understand whether its hurdles or thresholds are the right ones, but the idea is worthy of consideration.”

Under a Westminster-style system, a recall petition would have been triggered when former SNP children’s minister Mark Mcdonald was suspended from Holyrood for one month in 2018 for sexual harassment.

On Thursday, he announced he will stand down at the next Holyrood election. This means he will also qualify for an automatic resettlement grant of around £50,000.

Mr Mackay has not been suspended or convicted of any crime. But his downfall once again highlights an odd gap in Holyrood’s rules.

It might well be time to take another look at Mr Rennie’s plans.