WHEN it was announced that Ruth Davidson was to become a senior advisor to Tulchan Communications in London, the reaction was predictable. Here was the former leader of the Scottish Conservatives, already earning £63,579 as MSP for Edinburgh Central, set to make a hefty additional income of £50,000 for 24 days’ work a year.

In ordinary people’s language, that’s a month’s employment, or £2000-plus a day. As the first criticisms were voiced, Davidson insisted that she had done due diligence, and that this was not a lobbying position. Even so, the L-word hovered over her head like a cloud of sulphur, until the stench grew too toxic. Yesterday she announced her resignation from this contentious role, before she’d even set a foot under the desk.

Andrew Feldman, managing partner of Tulchan, who had so warmly proclaimed her signing, said that the firm supported her decision, and that “Scotland and the people of Edinburgh Central are lucky to have her”. For her part, Davidson said that when faced with the outcry at the “seeming incompatibility” of taking on this job alongside that of MSP, she felt obliged to choose between them. Not surprisingly, she opted for the role in which she has made her name.

It was a swift decision, possibly urged upon her by Tory HQ, and one that has doubtless rescued Davidson’s reputation, in the short term at least. While some are sceptical about the management consultancy that she set up with her partner earlier this month, seeing in it a hint of waning political commitment, it poses no threat to her standing. That said, as that company gets into gear, Davidson will have to tread carefully. After the recent embarrassment with Tulchan she will be under scrutiny, and understandably so. After all, her acceptance of Tulchan’s offer suggests her political – and indeed ethical – instincts are not as sharp as they could be.

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While the furore raged over Tulchan, Davidson’s attempt to appear guileless was misleading. Although she did not flout any parliamentary rule, there is a grey area between actively breaking the law, and operating in a dubious but not illegal manner. That lucrative appointment fell into this murky area, a zone patrolled not by lawyers but by those with good judgement. In other words, while Davidson had done nothing technically wrong, this did not mean her decision was right. It sent out the wrong signals. Hence calls for her resignation from Holyrood, and her hastily beaten retreat.

Davidson’s case might prove to be a one-week wonder, or so she hopes. Nevertheless it highlights a problem that needs to be more formally addressed. When a public servant accepts a supplementary and highly remunerated post it stirs old grievances. Suspicion is aroused over the motivations of every politician, reinforcing the fear that they are all opportunists, out for themselves. Most worrying is the perception that when they take on another position, their day job does not command their undivided attention. In effect, voters are served by part-timers.

This is grossly unfair to the majority, who work exceptionally hard for their salary. It is, however, indicative of the thin ice on which politicians walk. Any hint of two-timing inflames the belief that they aspire to be fat cats. This raw nerve often has the word Tory written through it, as if it were a stick of Blackpool rock.

But it is not an exclusively Conservative issue. Ian Blackford, leader of the SNP at the House of Commons, has also come under fire for his extra-curricular business interests. This work might represent no conflict of interest, but perhaps politicians of every stripe should observe the spirit of the law rather than the small print. In light of the Davidson debacle, should they not all put themselves beyond reproach by avoiding any additional paid work?

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No wonder Neil Findlay, Labour MSP, wants to pass a private member’s bill changing the law on MSPs having a second source of income. When parliamentarians hold high-profile, influential positions, they inevitably – and perhaps rightly – lay themselves open to the charge of feathering their nests by virtue of their proximity to the centre of power.

Because, make no mistake about it, Davidson was not hired for her abundant charisma, charm or chutzpah. Nor was it cleverness alone that secured this advisory seat. Foremost among her assets was her experience of the upper echelons of the political sphere, and her first-class contacts within it. When top politicians are head-hunted, it is their address book, their associates, the circles in which they operate, that set them apart. In this sense, there is nothing personal about it.

The view from the other side of the fence is more complicated. For Davidson, the financial reward was probably a factor, but there will have been other elements too. Anyone who has stepped down from a big job will know the feeling of being suddenly diminished. There can be a sense of becoming redundant or passe, of losing status and not commanding respect as before. To discover you are still in demand must be flattering and reassuring. Hence why Davidson probably leapt at this opportunity without pausing to consider if it was wise. In her own mind, doubtless, it was simply one small step in a series of manoeuvres, as she re-defines herself in the years to come. As of yesterday, she will have to be far more cautious in the way she proceeds.

For as long as a politician is paid to represent the people, that should be their main – arguably their sole – occupation. We live in self-centred times, becoming more so thanks to the clique in charge at Westminster, for many of whom political power represents a short cut to the overflowing pigs’ trough. If nothing else, the Davidson debacle will act as a cautionary tale for anyone tempted to follow her lead, north of the border at least.

Quite obviously, as Findlay recognises, the rulebook governing the conduct befitting parliamentarians needs to be rewritten. Only then will doubt or ambiguity over how to behave be removed. In the meantime, those who seek to advance their own financial interests while in office must not be surprised when brickbats are lobbed in their direction. As of now, such noisy protest should be the only special pleading acceptable at Westminster and Holyrood.