This is inconceivable. However, UKIP has an important influence on UK politics even if they only win a few seats in the sense that both major parties are mortal

This is inconceivable. However, UKIP has an important influence on UK politics even if they only win a few seats in the sense that both major parties are mortally afraid of loosing voters to UKIP. To avoid that, the big parties take some of UKIPs policies on board.