Nazanin Zaghary-Ratcliffe, a British-Iranian mother, was arrested in Iran in April 2016. Every day since has been a living nightmare for the Ratcliffes.

Now, after glimmering hope for a temporary release, Nazanin learns instead that the revolutionary guard wish to reopen her case. The ramifications? An additional 16 years in prison to add to her five year sentence.

The accusation that Nazanin is a spy has always been a ridiculous notion for her family and her employer. The UN call it arbitrary detention. But months of lobbying by her husband Richard Ratcliffe, has not so far convinced the UK Foreign & Commonwealth Office that this British prisoner is worth prioritising. And this is why.

The UK is a net importer. The value of its exports is pretty unimpressive, and is far exceeded by its imports. This leaves them with a trade gap of about £15.5bn.

Around half of these exports (as well as its imports) are down to the EU. But after Brexit, when Britain leaves the Union and possibly the single market, those exports are at risk.

While Britain and the EU remain at an impasse in negotiations Britain is scrambling for trade deals and Iran’s potential $600bn market is beyond appealing. An Iranian investment drive will mean infrastructure projects such as the expansion of its 10,223km long state-owned rail network, upgrades to all 54 of Iran’s airports and the construction of seven more.

And there is potential for UK companies to get involved in all of this.

The London Chamber of Commerce and Tehran Chamber of Commerce have already signed a memorandum of understanding to deepen trade between the two countries and eliminate barriers to trade. And the UK company Quercus recently signed a $600m deal with Iran’s Ministry of Energy to build a solar power farm in Iran.

Between January and October 2016 the value of UK exports to Iran had continued to rise and were 42% higher than during the same period in 2015. The UK certainly does not want that trajectory to change.

There are still risks associated with trading with Iran due to remaining US sanctions that some European banks are still liable to respect (or risk a fine) even after the Joint Comprehensive Plan of Action (JCPOA) in 2015. And now with Donald Trump threatening to decertify the JCPOA, further sanctions could return. Is it any wonder the British PM Theresa May was frantically on the phone to Trump to uphold the deal. But one might question whether May should be doing something similar although for very different reasons.

It seems that the Conservative government in the UK have allowed human rights to fall by the wayside at the prospect of lucrative trade deals. A trait they’ve demonstrated often enough.

Ironically it is not so long since May reportedly criticised Iran to Al-Riyadh, Saudi’s pro-government publication, for meddling in Arab countries; which Lord Lamont, the trade envoy to Iran, brushed off saying “trade is trade, politics is politics”.

Just how far exactly can this mantra hold. The line has always been that the UK would not intervene in cases of dual nationals (Iran does not recognise dual nationality) unless the circumstances were exceptional. But these are surely now exceptional circumstances. Even Rouhani has admitted that he has his own sensitivities when it comes to the cases of dual nationals in prison in Iran. He maintains however that he cannot get involved because of the independence of the judiciary, unless of course they were acting in contravention of the law. The UN has called Nazanin’s detention unlawful, so what exactly does it take for the President to get involved now?

Both the UK and Iran are contravening their own supposed policies on intervention. And the truth is that those who are interested in keeping Nazanin behind bars – the revolutionary guard – have their own thoughts about Iran increasing trade with the west. It is something they will resent.

In this case trade is very much political.

The UK government – the prime minister and the foreign secretary – must put pressure on their counterparts in Iran to place their own internal pressure toward a just outcome for Nazanin Zaghari-Ratcliffe. If that fails, there should be consequences, including bringing Iran before the international court.

At present the UK is offering no incentive for Iran to take action for Nazanin’s release. This makes the UK as complicit as her detainers.