The vice-chancellors' organisation Universities UK said the higher education sector understood the current pressures on public spending and was playing a key role in tackling many of the long-term challenges facing the economy.

BBC: Universities' annual funding reduced by ?398m

But a letter from Mrs May's private secretary to the prime minister's private secretary said the current rules were a "key tool in protecting the public against significant harm".

BBC: Passport control at Heathrow's Terminal 5