The sale of the Typhoon fighter jet to Saudi Arabia is among those being challenged (Picture: MOD).
Campaigners are set for a legal challenge over the Government's sales of arms to Saudi Arabia, amid allegations the weapons are being used to commit 'war crimes' in Yemen.
Campaign Against Arms Trade (CAAT) is challenging a High Court ruling given in July 2017 which concluded the sales were "lawful".
Thousands of people have been killed in Yemen's four-year civil war, with reports suggesting millions are on the brink of starvation.
The fighting between Iran-backed Houthi rebels and a Saudi-led coalition in support of the internationally-recognised government of Yemen continues after a breakdown in peace talks.
CAAT says UK fighter jets and bombs sent to Saudi Arabia are being used in the Yemen conflict are in violation of international humanitarian law.
At a hearing starting on Tuesday, CAAT will urge judges at the Court of Appeal in London to overturn the ruling.
Speaking ahead of the hearing, Andrew Smith from CAAT, said: "UK-made weapons have played a central role in the four-year Saudi-led bombardment of Yemen.
"The results have been catastrophic, with tens of thousands of people killed and vital infrastructure destroyed.
"We believe that these arms sales are immoral, and are confident that the Court of Appeal will agree that they are unlawful."
CAAT says more than 10,000 people have been killed in Yemen.
They added there is overwhelming evidence that UK arms sent to Saudi Arabia have helped create a humanitarian catastrophe, leaving 80% of the population in need of aid.
But the UK has continued to allow sales and has licensed over £4.7 billion worth of arms to Saudi Arabia since the bombing began in March 2015.
In 2017, two High Court judges rejected CAAT's challenge.
They decided the Secretary of State for International Trade had not acted unlawfully or irrationally in refusing to block export licences for the sale and transfer of arms/military equipment.
Secret evidence played a part in the case and the court delivered a closed judgment as well as a public ruling.
A Government spokesman said at the time: "We welcome this judgment, which underscores the fact that the UK operates one of the most robust export control regimes in the world.
"We will continue to keep our defence exports under careful review to ensure they meet the rigorous standards of the Consolidated EU and National Arms Export Licensing Criteria."
The appeal is due to be heard over three days.