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LONDON, England (CNN) -- A design student has come up with an invention he hopes will help eliminate drinks being spiked in bars.
Tom Martin, 23, has created the "Hollow" glass as part of his final year of a design degree at London's Brunel University.
The idea for the glass came after a friend was sexually assaulted when her drink was spiked in a bar last year.
He says the Hollow could stop future attacks happening because it is impossible to tamper with drinks in it.
Hollow has double walls -- the inside wall is lower than the outer one and the gap between the two is so narrow, a special nozzle has to be used to drop anything inside it.
The nozzle, which can be attached to any optic used to pour nips of spirit measures, sits on top of the drinking glass, filtering liquid into the walls of the vessel.
Once the optic is removed, it is extremely difficult to pour anything into the sides because the center is hollow and bottomless.
"If you were to drop anything into the glass, it would go straight through the middle. If any drug did land inside the walls of the glass, it would be such a low percentage that it wouldn't have an effect," Martin said.
"It's such a simple idea but it works. It could dramatically reduce the number of drinks that are spiked."
Initially, Martin wanted to create a device that would fit on tops of bottles, but he was beaten to the idea by another company, which created a rubber stopper called "Spikey" last year.
"The Hollow is good for wine drinkers. Lots of women drink wine and they are the main targets of having their drinks spiked," Martin said.
The Hollow sits on a mat, which changes color according to how long the drink has been left unattended. If the glass is not touched for 10 minutes, the color changes to blue, alerting the drinker that there may be a higher risk that it has been tampered with.
Martin hopes to turn his prototype into a commercial reality.
Brunel University School of Engineering and Design director Paul Turnock said the idea was simple but effective.
"With further development, this could be a stylish, new and safer glass being used in pubs and restaurants."
A spokeswoman for London Metropolitan Police would not comment specifically on Hollow. However, she told CNN the key to preventing drug-assisted assaults was for people drinking in public places to be aware of their drinks at all times.
"If they get up to dance, they should make sure someone in the group stays with and watches the drinks at all times." There were 785 reported cases of drug-assisted rape in London last year.