Last week, UK Prime Minister David Cameron announced a referendum on whether Britain should remain in the European Union, to be held in June. Though Cameron himself supports staying in the EU, his towheaded schoolmate Boris Johnson says it’s time to make a Brexit.

How did it come to this? We look back at a short history of the UK’s involvement in the EU to find out what’s changed since its inception in 1951, and whether the UK will lose much if it opts out.

1951

Following World War II, there is a movement to create a sense of unity between Germany and France, which ultimately lays the foundations for the European Union as we know it today over 40 years later.

The EU can trace its origins from the European Coal and Steel Community (ECSC) and the European Economic Community (EEC), formed in 1951 and 1958 respectively.

1952

The European Parliament is created. Along with the existing Council of Europe it works on passing EU laws. New legislation is put through either by consensus from members or qualified majority voting. Ultimately, this means a single state’s objection to a new piece of legislation makes no difference if the other 26 states are in favour of it. For a country like the UK, which values sovereignty so highly, this could grow to become an issue.

1964

The landmark case Flaminio Costa v ENEL in the European Court of Justice establishes the supremacy of European Union law over the laws of its member states. In the case, it was said that “member states [of the European Community] have limited their sovereign rights … and have thus created a body of law which binds both their nationals and themselves”.

1991

The European Union is formed as we know it today via the Maastricht treaty. The union is created to establish an economic and monetary union and establish a common foreign and security policy. The UK is one of the first members.

1997

The Schengen agreement is signed. This means the EU’s internal borders are abolished and the region is now a passport-free zone. Interestingly, the UK opts out of this agreement, preferring to maintain its own borders. This gives the UK the ability to opt out of EU asylum and immigration legislation it dislikes. It is one of the first signs of UK euroscepticism.

Research published in February 2016 from NatCen’s British Social Attitudes survey reveals 57% of British citizens believe immigration would be lower upon leaving the EU, and 47% believe Britain’s distinctive identity is undermined by the country’s membership in the EU.

1999

On January 1, the euro officially comes into existence. The UK does not adopt the euro, and it is free to control its own interest rate policy or adjust to a euro exchange rate.

2001

Greece joins the euro. From this point on, Greece’s involvement in the EU provides the UK with a range of problems. Although the UK is not part of the eurozone, a potential Greek exit from the EU would inevitably harm the British economy.

2004

The EU enlarges from 15 states to 25, bringing 73 million people to the union and moving its borders considerably further east. According to the EU Observer, this “big bang” enlargement has a significant impact on the EU itself, with new member states bringing “their own preferences and interests to bear, thereby complicating in some cases the already fractured foreign and security policies of the EU”.

2006

It is announced that 45% of overall EU spending is going towards the Common Agricultural Policy. This is almost half EU spending towards an industry that only employs 5% of EU citizens and generates 1.6% of GDP. This is no doubt a frustrating statistic for member states, and adds to the UK’s growing disillusionment with the EU.

(British Minister of State for Employment Priti Patel believes leaving the EU will cut the cost of the price of food, because “the Common Agricultural Policy has inflated the price of food”.)

2007

The Lisbon treaty is signed, which gives greater power to Brussels by creating the first president of Europe, as well as a European foreign minister, and ends Britain’s right to veto new EU rules in more than 40 policy areas. The EU is also given power to set immigration policies for all 27 members and to rule on criminal policy. When the bill becomes law in 2009, William Hague, the shadow foreign secretary at the time, says it is “a bad day for British democracy”.

2011

In December, leaders of the 17 eurozone countries agree to sign a new intergovernmental treaty mandating greater fiscal co-ordination and budget discipline. This attempts to offer a long-term solution to the ongoing eurozone sovereign debt crisis. At this stage, the UK stands to gain or lose enormously depending on whether the euro succeeds or fails and has little control of the outcome.

More than 50% of the UK’s trade is done with the EU and, at this stage, a deep recession in the EU would have a major impact on the demand for goods and services in the UK.

2013

David Cameron makes referendum pledge by promising an “In-Out” referendum if he wins the 2015 general election, which he does. But Cameron continues to be a staunch supporter of UK membership in the EU, arguing in years to come that he has “no doubt in [his] mind [the UK] are better off in a reformed EU and [they] have got to make that argument right across the country”.

2016

In February, Cameron spends two days in talks in Brussels with other member states and their leaders, agreeing to a package of changes to the UK’s membership. The negotiations face criticism from Justice Secretary Michael Gove, who believes they are not “legally binding”, but this is counter-acted by Attorney-General Jeremy Wright saying, “It will have legal force from the day on which we indicate after a referendum that we wish to stay in the European Union.”

Cameron also announces a referendum for June 23, so that Britons can decide for themselves where they stand on the issue.