Mozambique's President Filipe Nyusi on Tuesday asked London’s High Court to block allegations he accepted unlawful payments in the country’s lawsuit against Credit Suisse and others in the $2bn “tuna bond” scandal.

The tuna bond, or “hidden debt”, case has triggered criminal investigations from Maputo to New York, plus a series of lawsuits in London involving Credit Suisse, shipbuilder Privinvest, its owner Iskandar Safa and many others.

Mozambique, one of the world’s poorest countries, wants to revoke a sovereign guarantee on a loan it has alleged was corruptly procured and secure compensation for other alleged wrongdoing.

But the cases in London have been mired in difficulties in advance of a trial scheduled for October as Mozambique’s repeated failure to disclose key documents has threatened to derail the litigation.

Privinvest and Safa are trying to drag Nyusi into the case, arguing he should contribute to any damages they may be ordered to pay if they are found liable to Mozambique.

Their claim against Nyusi focuses on payments of $11m they say Privinvest made in 2014 to fund Nyusi’s successful run for president and his ruling Frelimo party’s election campaign.
Privinvest and Safa have argued that if the payments were not lawful and they are liable to Mozambique, then Nyusi should be liable to them.

Nyusi, however, has said he is entitled to immunity as a sitting head of state. He was not in court on Tuesday but his lawyer, Rodney Dixon, argued that there was “no difference as a matter of law” between someone trying to sue Nyusi in London or The United Kingdom’s King Charles in Australia.

Nyusi’s bid for immunity is the latest twist in the long-running dispute, centred on three deals between state-owned companies and Privinvest, ostensibly to develop Mozambique’s fishing industry and for maritime security.

The deals were funded in part by loans and bonds from Credit Suisse since taken over by UBS and backed by undisclosed Mozambican government guarantees.

But hundreds of millions of dollars went missing and, when the state loan guarantees became public in 2016, donors such as the International Monetary Fund halted support, triggering a currency collapse, debt crisis, and years of litigation.