Explainer - What you need to know about Gibraltar in Brexit talks

FILE PHOTO: Tourist binoculars offer users the chance to pay in pounds or euros, on top of the Rock in the British overseas territory of Gibraltar, historically claimed by Spain

MADRID (Reuters) - Spain is threatening to oppose a deal on Britain's withdrawal from the European Union unless it gets assurances over the disputed peninsula of Gibraltar.

Unlike the much-discussed issue of avoiding a hard border on the island of Ireland, not much has been said publicly about Gibraltar during tense months of Brexit talks.