Bribes, they come in all sorts of shapes and sizes.

They can be big and they can be small. And, despite the cliche, they far from always arrive in brown envelopes.

Scotland’s warring political tribalists routinely accuse each of other’s heroes of corruption, usually on social media and almost always without so much as a whiff of evidence.

Yet, drown out the very online noise, and there really are cases of bribery in our country, in both the public and private sector. And there are also a fair few examples of Scottish firms or their staff offering backhanders abroad.

Unusually for Scottish and British law - this is a crime which you can be punished for at home if you commit it abroad.

So what happens to those who give and take kickbacks? At least those who are caught? Well, sometimes they get the jail. Sometimes they pay big fines.

Police and prosecutors do go after bribers, big and small.

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Take Desmond Tough. He worked for Aberdeen City Council valuing council houses being sold off for right-to-buy.

Back in 2017 he was jailed for 18 months for taking payments of between £75 and £500 to cut the value of properties.

Or Weir Group. Way back in 2010 the Glasgow-based engineering giant had to pay a fine of £3m and had nearly another £14m confiscated as proceeds of crime.

Somebody working on behalf of the PLC had paid kickbacks - using cash an oil-for-food programme designed to help starving children - to get a deal in Saddam Hussein’s Iraq in the early years of this century.

The UK’s 2010 Bribery Act, which came in to force just after the Weir case, allows for the prosecution of those who pay bribes, those who receive them and - and this is rather important - companies which fail to prevent bribery.

But in law enforcement there is more than one way to skin a cat. The criminal court is not the only means of ensuring bribery does not pay.

Since the law came in to force there has been a special, theoretically temporary measure in place. Firms have been encouraged to self-report bribery - and, potentially, make a settlement under civil proceeds of crime proceedings.

This is not necessarily a get-out-of-jail card. Prosecutors - in Scotland, the Crown Office and Procurator Fiscal Service - can still decide the case merits a criminal charge.

Official guidance published by the Crown stresses that officials at its Serious Organised Crime Unit will be checking to see whether, for example, senior executives connived with bribe givers or takers.

This “self-reporting initiative” is currently due to expire at the end of June. The Herald on Sunday asked the Crown Office whether the deadline would be extended, as it has been before. Officials said this would be a matter for law officers.

Ask things stand, firms have three months to fess up to bribery under the scheme. Crucially, there is little prospect of avoiding publicity if they do, “unless there is a compelling reason for confidentiality”. Any settlement, according to Lord Advocates guidelines, has to be officially recorded.

Provided senior prosecutors sign off on it, such self-reported bribery cases are handed to the Civil Recovery Unit, the small, low-profile team of lawyers and investigators who chase dirty money through the courts on behalf of the Scottish Government.

As The Herald reported yesterday, the CRU sees its main mission as “disrupting" organised crime. The unit can pursue targets through the civil courts for the proceeds of crime even if they have not been convicted of a criminal offence.

But CRU also has another job, to settle with companies who have found they have benefited from bribery - even of they did not initiate the criminal conduct.

The best know example of this came in 2021 when Wood - the Aberdeen-based oil and gas engineering giant - agreed to hand over nearly £6.5m in profits it made from contracts in Kazakhstan.

Wood had not paid bribes. But in 2017 it launched an internal inquiry in to a business it had acquired, PSN, which had a joint venture in the energy-rich central Asia nation. The investigation discovered payments of more than £8m to an intermediary but found “limited evidence” of any services provided in return.

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The Aberdeen giant’s then chief executive, Robin Watson, said the behaviour had been “unacceptable”. He added: “While we didn’t own the business until 2011, we take responsibility for dealing with the consequences and have taken steps to further strengthen our culture and processes to ensure it does not happen again.”

Back in 2021 Wood said it was setting aside more than $150m to settle bribery cases involving businesses it had acquired with authorities in the UK. US and Brazil.

The Scottish Crown office and CRU work closely with the Serious Fraud Office in England and Wales which handles self-reported cases down south. But Scottish-HQed businesses should apply to authorities north of the border even in respect of alleged bribery that took place overseas.

Firms which use the self-reporting mechanism have to show they have carried out their own investigation in to bribery. And they have to agree to fund a second probe carried out by independent forensic accountants appointed by the CRU.

But firms which self-report and face CRU investigation are not necessarily exposed to corruption risk abroad. There are purely Scottish cases too.

One involves a firm which handed over thousands of pounds worth of profits from business obtained by a third party who give out holiday vouchers to officials making purchases.

Anne-Louise House, head of the CRU, told The Herald on Sunday that around half the self-reported cases involved allegations of bribery abroad.

But just a few big foreign cases can account for a big chunk of the CRU’s financial haul - if not of its core business of chasing ill-gotten gains.

The Wood payment alone , for example, accounts for nearly a tenth of the £68m the unit has recovered since it was set up 20 years ago. All the money raised goes to a special pot, CashBack for Communities, used to find good causes, especially for children and young people. “Some of the self-reported [bribery] cases,” Ms House said, “are quite valuable and they can cause a spike in the figures."

Crown sources stress that self-reporting is designed to ensure that kickbacks are not brushed under the carpet. “It is part of COPFS's commitment to encouraging good corporate governance and to creating a corporate culture in which bribery is not hidden,” the Crown said.