Most I'm sure know Gibraltar was handed to Britain after a military defeat, it's "possibly" right we should think of giving it back, as we shouldn't keep extremely old military grudges against a new neighbour.
BUT it obviously isn't as simple as that - as there has been a lot of history since, and the people living there don't feel Spanish, time has moved on, the place has developed it's own cultural and social identity etc etc.

In short as we're all part of the EU, it shouldn't matter who on paper owns the place.

Now Spain causes a hugely expensive security headache to the entire EU by owning two parts of North Africa. In law, since they are Spanish, it means the EU has a land frontier against Morocco, and this as you can imagine is a magnet to anyone wanting to sneak into Europe.

We should state to Spain we will agree to talks about the sovereignty of Gibraltar (Talks mind, nothing else, they can talk all they want, we can provide the tea, they can bring the custard creams) WHEN they return Ceuta and Melila to Morocco.