I assumed it was a literary reference to Blake: I will not cease from Mental Fight, Nor shall my Sword sleep in my hand: Till we have built Jerusal

I assumed it was a literary reference to Blake: I will not cease from Mental Fight, Nor shall my Sword sleep in my hand: Till we have built Jerusalem, In England's green & pleasant Land. The British, broadly speaking, are familiar with this quotation (the poem was set as a popular hymn); when they refer to the climate as pleasant, it's somewhat tongue-in-cheek.