A British Union flag flies in Gibraltar, on 09 August 2013. Reports state that tension was running high on 09 August 2013 between Spain and Britain over an artificial reef at Gibraltar, with Madrid saying it reserved the right to take ‘legal and proportionate’ measures to defend its interests. British warships were meanwhile due to set sail for Gibraltar in what Spain and Britain described as a routine military exercise. Image Credit: EPA

What is the source of the current row?

Spain is objecting to the construction of an artificial reef on the northern end of the territory, which consists of a collection of sunken wrecks and concrete blocks designed to give marine wildlife an environment to breed and colonise, and boost tourism. Madrid says the reef will affect the catch of local Spanish fishermen. Gibraltar says one boat in particular has over-fished the area, and decided to enforce a 1991 law banning fishing to the letter.

How has Spain shown its anger?

Tension has flared several times over the past nine months. Gibraltarians said Spanish police motor boats have interfered with pleasure craft. A 10,000-strong petition was submitted calling on the Government to take a firmer line with Madrid. In February, a Spanish warship entered British water for 20 minutes where it was confronted by the Navy and asked to leave. At the end of July, residents and tourists had to endure three days of delays at the border as a result of increased vehicle searches by the Spanish authorities. Spain’s foreign minister has now threatened to impose an entry fee of 50 euros to cars entering from Gibraltar.

Haven’t we been here before?

The rock has been disputed by Spain ever since Britain captured it in 1704, but relations have rarely been this bad since the Second World War. Still, under Gen Franco’s dictatorship the frontier to the mainland was closed in 1969 for 16 years.

What do the Gibraltarians say?

The 30,000 locals say that Madrid is just trying to distract from its woeful economic problems. They are determined to remaining a British Overseas Territory. They may be bi-lingual, but in two non-binding votes, in 1967 and 2002, 98-99 per cent voted in favour of saying British.

Why is the territory so important to Britain and Spain?

Situated at the entrance to the Mediterranean, the limestone outcrop on the southern tip of the Iberian Peninsula has a prime strategic location and is home to a British naval base. It was a key point in the anti-submarine campaigns in both World Wars. They may be EU partners, but Britain is loathe to yield any ground, as it would set a bad precedent for other Overseas Territories, while Spain wants to reclaim land that belonged to the kingdom of Castile.

—The Telegraph Group Limited, London 2013