There is an article in today's edition of The Guardian speculating that, since a second Brexit referendum would require appropriation of money from HM's Treasury, PM Theresa May would be constitutionally entitled to ask the Queen to withhold royal assent to any referendum bill passed by the House of Commons without the backing of the government.
Frankly, I find that scenario unlikely, but, just for the sake of argument, if it came to that, would the Queen do it ? It would be the first royal veto of legislation in the UK since 1707 and could potentially trigger a major constitutional crisis and even calls for the abolition of the monarchy.
BTW, the suggestion that a royal veto could be on the cards came from
Sir Stephen Laws , who formerly served as the First Parliamentary Counsel to the British government, so, as far-fetched as it may sound, it is not a loony proposition.