Briefly outline what prerogative powers are

Exercised in the name of the Crown (historically stemming from the monarchical use of these powers), they may encompass an array of sovereign powers including the right to go to war, dissolve parliament, unmake and make treaties or even bestow knighthoods. Royal prerogative powers or just prerogative powers are challengable by judicial review, as famously established by Lord Denning the GCHQ case.