BRAIN: From the first sip, alcohol is absorbed into the bloodstream and reaches the brain. Although you won’t be aware of it, there is an impairment of brain function, which deteriorates further the more you drink. Cognitive abilities that are acquired later in life, such as conduct and behaviour, are the first to go. Early on you will experience mild euphoria and loss of inhibition, as alcohol impairs regions of the brain controlling behaviour and emotion. Most vulnerable are the brain cells associated with memory, attention, sleep and coordination. Sheer lack of mass means that people who weigh less become intoxicated more quickly, and women will feel the effects faster than men. This is also because their bodies have lower levels of water.

HEART: Your pulse quickens after just one unit. Alcohol is a vasodilator – it makes the peripheral blood vessels relax to allow more blood to flow through the skin and tissues, which results in a drop in blood pressure. In order to maintain sufficient blood flow to the organs, the heart rate increases. Your breathing rate may also speed up.

8pm Five Units: Whose round is it then?

DIGESTIVE SYSTEM: The Government advises men to drink no more than three to four units a day and women no more than two to three, so after two pints of normal-strength beer (four units) or a large glass of red wine (3.5 units) we have already exceeded our healthy guidelines. The alcohol is absorbed through the stomach and small intestine and if you are not used to it, even small amounts of alcohol can irritate the stomach lining. This volume of alcohol also begins to block absorption of essential vitamins and minerals.

SKIN: Alcohol increases bloodflow to the skin, making you feel warm and look flushed. It also dehydrates, increasing the appearance of fine lines. According to Dr Nicholas Perricone, a dermatologist, even five units will lead to an unhealthy appearance for days.

11pm 10 Units: Sorry, what was your name again?

LUNGS: A small amount of alcohol speeds up the breathing rate. But at this level of intoxication, the stimulating effects of alcohol are replaced by an anaesthetic effect that acts as a depressant on the central nervous system. The heart rate lowers, as does blood pressure and respiration rates, possibly to risky levels – in extreme cases the effect could be fatal. During exhalation, the lungs excrete about 5 per cent of the alcohol you have consumed – it is this effect that forms the basis for the breathalyser test.

1am 15 Units: Let me tell you about my ex…

LIVER: Alcohol is metabolised in the liver and excessive alcohol use can lead to acute and chronic liver disease. As the liver breaks down alcohol, by-products such as acetaldehyde are formed, some of which are more toxic to the body than alcohol itself. It is these that can eventually attack the liver and cause cirrhosis. A heavy night of drinking upsets both the delicate balance of enzymes in the liver and fat metabolism. Over time, this can lead to the development of fatty globules that cause the organ to swell. It is generally accepted that drinking more than seven units (men) and five units (women) a day will raise the risk of liver cirrhosis.

3am 20 Units: Where am I? I need to lie down

HEART: More than 35 units a week, or a large number in one sitting, can cause ‘holiday heart syndrome’. This is atrial fibrillation – a rapid, irregular heartbeat that happens when the heart’s upper chambers contract too quickly. As a result, the heartbeat is less effective at pumping blood from the heart, and blood may pool and form clots. These can travel to the brain and cause a stroke. Atrial fibrillation gives a person nearly a fivefold increased risk of stroke. The effect is temporary, provided heavy drinking is stopped.

BLOOD: By this stage, alcohol has been carried to all parts of the body, including the brain, where it dissolves into the water inside cells. The effect of alcohol on the body is similar to that of an anaesthetic – by this stage, inhibitions are lost and feelings of aggression will surge.

The morning after: Can you please just shut up…

BRAIN: Alcohol dehydrates virtually every part of the body, and is also a neurotoxin that causes brain cells to become damaged and swell. This causes the hangover and, combined with low blood-sugar levels, can leave you feeling awful. Cognitive abilities such as concentration, coordination and memory may be affected for several days.

DIGESTION: Generally, it takes as many hours as the number of drinks you have consumed to burn up all the alcohol. Feelings of nausea result from dehydration, which also causes your thumping headache.

KIDNEYS: Alcohol promotes the making of urine in excess of the volume you have drunk and this can cause dehydration unless extra fluid is taken. Alcohol causes no damage or harm to the kidneys in the short term, but your kidneys will be working hard.

One year on: Where did it all go wrong?

REPRODUCTIVE ORGANS: Heavy drinking causes a drop in testosterone levels in men, and causes testicular shrinkage and impotence. In females, menstrual cycles can be disrupted and fertility is affected. Studies have shown that women who drink up to five units of alcohol a week are twice as likely to conceive as those who drink 10 or more. It is thought it may affect the ability of the fertilised egg to implant.

BRAIN: Over time, alcohol can cause permanent damage to the connection between nerve cells. As it is a depressant, alcohol can trigger episodes of depression, anxiety and lethargy.

HEART: Small amounts of alcohol (no more than a unit a day) can protect the heart, but heavy drinking leads to chronic high blood pressure and other heart irregularities.

BLOOD: Alcohol kills the oxygen-carrying red blood cells, which can lead to anaemia.

CANCER: Excessive alcohol consumption is linked to an increase in the risk of most cancers. Last week, Cancer Research UK warned how growing alcohol use is causing a steep rise in mouth cancer cases.

PANCREAS: Just a few weeks of heavy drinking can result in painful inflammation of the pancreas, known as pancreatitis. It results in a swollen abdominal area and can cause nausea and vomiting.