There's just too much to remember at this time of year. When you're in the middle of Christmas shopping, you're working hard enough trying to recall what you bought Great Aunt Gladys and Uncle Bob last year, without having anything else to bear in mind. In most cases, when we nip back to the car to drop some of the heaviest things off, it's hard enough to recall where we parked, let alone consider the wider implications of what we're doing.
However, the experts are warning that a failure to consider the consequences could cost us £263.
The riskThis is the sum that M&S Bank has come up with. It has calculated that the average person makes two main trips to the shops to collect their festive goodies. The combined spend for both trips is set to total £526, which includes £347 on gifts and £179 on food and drink. It means that each time, we have a car boot filled with an average of £263 worth of things.
It also reckons that for the majority of people, today is likely to be one of the days we make the trip (the other one is Saturday 22nd December when we're going to be hunting for the food), so it's warning people to think about the safety of the car boot stuffed with goodies.
Not coveredMost car insurance policies will cover you for items left in the car up to a particular value. However, some do not - and instead have it as an optional extra that you have to pay more for.
Some have relatively low limits, which won't cover the value of a typical Christmas shop. Monetos says that the typical sum covered by this insurance tends to be £150 - which will clearly fall short for many. Meanwhile, some will have a limit - such as 10% of the total value of the car - which could cause problems if you are driving an older car.
Before you set out, it's worth checking what cover you have. Neil Rogers, head of insurance at M&S Bank, said: "Unfortunately this time of year does mean the car boot can become a target for opportunistic thieves, so it's important to make sure you've got adequate vehicle contents cover for your Christmas shopping." His policy, for example, covers £200 of contents, plus £300 of additional shopping if it comes from M&S.
Protect yourselfOf course, the best protection is prevention, so he says it's also essential to take precautions to ensure your car is safe.
His advice is to keep shopping bags covered and locked in the car boot - they could be tempting for opportunistic thieves if left visible to passers by.
Don't leave expensive electrical items in view - make sure mobile phones and GPS devices are safely locked away or removed from the vehicle.
Don't make it easy for thieves - be sure to fully close all windows and roof panels and always lock the vehicle, even if you're just getting a ticket for the car park.
Don't leave receipts in shopping bags - so you've got them to hand should the worst happen.
Advice from Zurich meanwhile stresses that you need to ensure you have a list of items left in the car, and that you can account for them. Your shopping list and receipts would be ideal.
The experts there also say that each time you lock up you should check that the car has been properly locked - especially if you have done it with a key fob. The British Crime Survey reveals that thieves got access to a car through an unlocked door in more than a third (34%) of incidents of theft from vehicles.
You should also consider where you park - try to find spots in well lit areas where people will be able to see anyone interfering with your vehicle.
Steve Gilbert, personal lines technical underwriting manager at Zurich, said: "It can be a pretty distressing experience finding your car has been broken into. There's the financial loss, as well as the added misery of when something irreplaceable or sentimental is stolen. It is vital that car owners don't leave their possessions on show. Thieves don't need an added invitation to break into your car so don't give them one."