LONDON - One unnamed British woman was killed in Wednesday's deadly assault on Tunisia's national museum, Britain's Foreign Office said on Thursday, denouncing the incident as a cowardly and despicable 'terrorist attack.' Gunmen wearing military uniforms stormed the museum on Wednesday, killing 20 foreign tourists and three Tunisians in one of the worst militant attacks in a country that had largely escaped the region's 'Arab Spring' turmoil. 'The Tunisian people are rightly proud of their democratic transition,' British Foreign Secretary Philip Hammond said in a statement, confirming the British woman's death. 'Cowardly attacks, such as the one we saw yesterday, must not be allowed to undermine what they have achieved.'