EU Dinner
The EU dinner will be everything but informal. (Reuters)

By 7 p.m. this evening local time, the British Prime Minster will be sitting down to a dinner with the leaders of the EU and start 24 hours of negotiating to get the best possible deal for the UK.

Dr Harry Witchel, a psychobiologist at the University of Sussex, near Brighton, is an expert on body language, specifically the territorial nature of the human species. He gives his advice to the Prime Minister ahead of the dinner.

Speaking to the International Business Times UK, Dr Witchel said there are four things for the Prime Minister to be wary of when he enters the dining room in Brussels this evening.

1. Know when to bring up the agenda

"Unlike most dinner parties, the people who go to the EU summit will have a specific agenda on the table - to save the euro," Dr Witchel said. "The Prime Minister, however, should keep the conversation as light as possible when it comes to the dinner and speak to those to his left and right through most of the meal. According to a theory called proxemics, if anyone speaks to someone four metres away or further, it sounds formal, which can give off the wrong impression at a dinner table, depending on how well you know that person.

"Only towards the end of the meal, when people have had a bit to drink and their bellies are full, should there be any discussion about deals and negotiations, as people are far more euphoric with food inside them compared to at the beginning of the evening."

2. There are lots of people

"I don't know how anyone will be able to control so many people of this kind, as all of them will be used to commanding a room on their own accord," Dr Witchel said. "This can quite often mean that many people will be jostling for position in a territorial manner, which could well come across as arrogant.

"To avoid the problem, if I were the Prime Minister, I would ask an aide to speak to Mrs Merkel or Mr Sarkozy about sensitive subjects before the dinner, rather than bring them up himself. Essentially, Mr Cameron cannot be seen to grandstand."

3. There is a mixed gender but not a gender balance

"This is the worst case scenario for any dinner party," Dr Witchel said. "Normally, people at parties try to strike a balance between females and males and say things that are attractive and nice to other people. This encourages a bit of flirting, which makes people feel good about them.

"There will be a mixed gender at the EU dinner, but not a gender balance, which will mean that people will change the tone of their voices with different people from conversation to conversation. It will disrupt the whole flow of the evening and Mr Cameron needs to be aware of this."

4. Everyone will know each other but not necessarily be friends

"This is the worst of both worlds," Dr Witchel said. "Normally, for a dinner you invite your friends or two groups of different friends, which places you at the centre of social power, as you have introduced two sets of people to each other. In contrast, this will be an occasion where not only does everyone already know each other, but they may not even like each other. It will be like a sharp stick in the eye.

"Under no circumstances can Mr Cameron be seen to be distant, or he will come across as arrogant and snobby."