On a Monday afternoon in a bamboozling warren of offices next to the Palace of Westminster, Caroline Lucas is in yet another hurry. Forty-five minutes into the first part of our conversation, she reminds me that she has to sprint to the House of Commons to make sure her voice is heard in a debate – this time about Iran’s attack on Israel, and the RAF’s role in shooting down some of the drones involved. As usual, there is an inescapable obligation to fulfil: as the sole Green party MP, she says, she has no choice but to be there....