[Typo3] Clearing cache tables

[Gunnar Jonsson]

I am trying to clear the cache automatically at midnight, by introducing the 
following into the Typoscript template:

config.cache_clearAtMidnight = 1
config.cache_period = 86400

However, the cache tables are NOT cleared at midnight. It seems that nothing 
is happening.

Could someone tell me what I have missed ? Is it something more I have to do 
in order to get the cache tables cleared at midnight ?

Regards,
Gunnar Jonsson