Oh so we're into full ASB territory are we? So anything goes?
So let's have it that Spain attacks the Rock, but gets caught up in very stubbon fighting. The UK forces become besieged in the great fort, whilst the Spainards have to endure the hatred of the locals.
Spain is condemned by the world. NATO, considering Spain isn't a member, warns Spain to withdraw or face possible military intervention. France, not being a member of NATO per se, says it's going to stay out of it. So the BAOR can't drive across France & invade from the north.
PM Maggie losses her temper in utter frustration & calls in the RAF & RN. She orders the destruction of Madrid if Spain doesn't withdraw with 24 hours. Immediately thereafter PM Maggie goes on TV & announces that Madrid will be destroyed by a nuclear weapon if Spain doesn't cease their invasion & withdrawal. The Spainish thinks she bluffing & ignore her demands, but alerts their airforce to the threat just in case.
24 hours later, the RAF bomber goes into Spainish territory, but is shot down. Soon, thereafter, the Spainish govt realises Maggie wasn't bluffing & decides to withdraw. Unfortunately for Spain, PM Maggie (ignorant of the Spainish govt's new decision) orders the RN to launch the back-up plan & a SLBM is fired at Madrid. 10 miniutes later Madrid explodes in a nuclear fireball destroying the city not to mention the Spainish govt.
The Spainish fighting in Gibraltar immediately withdraw should the rest of Spain be consumed in nuclear flames.
The Apes of Gibraltar just watch on in total fascination wondering why the humans act so funny. Afterall, the Rock belongs to the Apes or don't these humans realise this?