Unambiguous, free and informed consent

Consent is understood:

• to have been freely given. In other words, the data subject was not pressurised to say "yes";
• to be specific, meaning that the consent relates to a well-defined processing operation;
• to be informed. The data subject has received all useful information about the planned processing.

It is not necessary for the consent to be given in writing, but oral consent does create problems with the burden of proof in case of difficulties.