Postal Letter

How can customs or post office people find out if there are medicines in envelopes as letters?

Say for example i was to send a letter with few pills of valium or simmilar medicine. How can customs or the post office people (royal mail UK) identify such things? . If the package is discreetley packged and there is no rattler noise & it's not chunky but just like a letter then there is no way for them to be seized right?. Any opinions or anyone done anything similar? Thanks!.

Public Comments

1. Some mail, is actually x-rayed. Also giving pharmaceuticals to folks they are not prescibed to is not just illegal it is dangerous. Your friend could have an allergy to the medication and it could kill them.
2. The US and the Royal Mail can open any letter or package. At any time for no reason. They are looking for bombs and germs and people mailing drugs. They use drug sniffing dogs and x ray machines and anything else they can think of. So does this sound like a good plan. NO.