Can you spot the missing word in this Daily Express headline? 'The majority of Brits now support an EU exit - so why no referendum?'

'The majority of Brits now support an EU exit - so why no referendum?'

The missing word is "that's" and it should be placed between "so" and "why". Thus the headline should properly read:

'The majority of Brits now support an EU exit - so that's why no referendum?'

The Daily Express article is here.