If the European Union is a school class, Denmark and the UK have always been best mates sitting on the back row – Denmark as the younger, who didn’t always abide by the rules, and the UK as the older, who tried to rewrite them (the future is unwritten, as Joe Strummer said).

This has been the case since 1973, when we joined the then European community together. The timing was no coincidence. Denmark applied for membership in 1961, but then withdrew when the UK was rejected. Only when times changed and our older friend was allowed to join the class did we take the step as well.

All along, Denmark and the UK have exchanged culture, people and goods. Sometimes for better (Top Gear, Christian Eriksen and bacon); sometimes for worse (EastEnders, Nicklas Bendtner and Marmite).

In terms of people, 17,000 Brits live in Denmark and there are about 30,000 Danes who currently call your rainy island home too. Maybe it’s our love of beer and grey weather that unites us more than anything.

In the European Union, though both sometimes grumpy and demanding members, we always stuck together. We both wanted monetary stability, but not the euro. Denmark wanted the safety of the EU umbrella, but not to be part of defence policy. The UK wanted to be in the single market, but equally wanted to have more control over its borders by opting out of Schengen. We both have unique justice and home affairs opt-outs. We had a pretty good deal – some might say the best – but then the UK went one step further.

On 23 June 2016, our best friend announced its decision to drop out of school. When you decided to quit, your economic growth was top of the class. Today it is 28th. Back then, sterling was doing reasonably well – today it is dropping. You said you wanted to write your own rules, but my friend, in the EU you helped write rules for more than 500 million people.

We’ll never compromise our principles to rescue the Tory party from Brexit, says Guy Verhofstadt

Together we worked to liberalise the internal market, ensuring free trade across borders, leading to both peace and prosperity in Europe. Due to our historical ties as free trading nations, we knew that our friend would always help us fight protectionism and thereby boost innovation and reduce consumer prices.

On climate change, the UK has also been a strong and reliable partner for Denmark. Together we have worked to increase the EU’s green ambitions and reduce our CO2 emissions, so that future generations have clean air to breathe and water to drink.

Together with Sweden and the Netherlands, Denmark and the UK have been aligned on about 88 per cent of EU votes in the Council and the European Parliament. If you leave us, our voice will be significantly diminished, and our combined efforts to cut red tape and bring common sense to the EU will be weakened.

A recent study found that none of the remaining EU countries see Denmark as their closest ally. Since June 2016, Danish ministers have therefore travelled the continent looking for new friends – with limited success. Unfortunately, the lack of success is quite logical, given our historical friendship with the British rebel.

In fact, we are both rebels. But in school, you cannot always have benefits without the associated costs, the good grades without doing the homework. So, UK, as your best mate at school, I’m saying to you: please don’t drop out. You still have friends here who look up to you and respect you. If there ever comes a time when you feel like changing your mind, you can always come back to class. But don’t leave it too late.