The building housed about 60 personal computers (PCs), mostly machines manufactured by Dell. But the thieves clearly knew what they were looking for and only selected the company's 15 IBM PCs, which have a higher value on the second-hand market. They loaded the machines into a waiting vehicle and made off.
This was not an isolated incident. Over several months, a number of companies on the same estate have been raided. At one, where the thieves were equally selective, the company duly replaced the machines. Four weeks later the thieves stole the replacement PCs.
'PCs seem to be the thing to steal at the moment,' Detective Sergeant David Harding, of Thames Valley Police, says. 'We have found it a massive problem.' The Thames Valley is particularly affected, given the number of suppliers and data processing centres in the region. But the problem is nationwide and growing.
There are obvious reasons for this, not least the fact that there are so many PCs in use. Almost all businesses now have them, as do many homes. Today's machines do not take up the whole of the desktop. They are lighter and easier to carry.
If the thieves know what they are looking for, peripherals can also be a target - a laser printer is a valuable piece of equipment. Many people now carry laptop PCs around with them and these are particularly vulnerable.
There is also a ready market for the stolen machines. Some of the thefts are opportunistic, with the thief unsure and unconcerned whether the PC he has just nicked is worth pounds 600 or pounds 6,000, but much of the crime is organised. Some stealing is clearly to order, DS Harding says, with IBM-compatible PCs and Apple Macs among the most popular.
Many are going abroad, with Nigeria, the Middle East and central Europe known destinations. Sometimes thieves do not bother taking the keyboards, which suggests that these machines are for export.
Others find their way on to the second-hand market. At a recent computer auction, a check of serial numbers by Thames Valley Police uncovered machines from three separate break-ins.
What can be done to prevent PC theft, beyond the basic measure of making premises more secure? The answer is quite a lot, although most users do nothing.
The computers can be indelibly marked with a stamp or pen. Following a spate of thefts in Salford, the Greater Manchester Constabulary set up a scheme that allowed users to have their postcodes stamped on terminals with a device like a branding iron.
PCs can be chained to a desk or wall. This may not be subtle, but it is fairly effective. There are security companies which provide reasonably unobtrusive, coated chains for this purpose.
PCs can also be tagged. This method is similar to the electronic tagging of goods in a shop. If the tag passes through the sensors, an alarm is activated. Of course, this only works if the PC is carried through the sensors; if it leaves by a route other than the front door, the tagging will have been in vain. The tag can be placed inside the PC so the first the thief might know about it is when the alarm goes off.
With laptops, it is common sense not to let the machines out of sight and not to leave them visible in an empty car (as happened at the time of the Gulf war, when a laptop containing sensitive defence information was stolen). An effective safeguard is to carry them in a briefcase.
Many companies do not seem too troubled by the thought of losing their PCs. After all, the machines are insured. But it is not just to do with the cost of the hardware. When someone removes a PC they also take any software and data on the machine - plus any work in progress, which can be particularly irritating if no recent back-up has been made. Suppliers can be lax as well. They could easily give their PCs a unique, indelible identity number at the time of manufacture, rather than a removable serial number as at present - although in fact most thieves do not bother to detach the serial numbers because most users do not keep a record of the numbers of their PCs.
Stolen PCs are virtually untraceable if the serial number is unknown, and most police forces will not even record the details in their stolen property lists. If the machines were bought direct from the manufacturer, the latter might have a record of the numbers, but few distributors maintain this information. If the insurance companies started to demand the serial numbers of stolen machines then this might change. But while users fail to take basic precautions, the number of PC thefts will continue to rise.