FO-3 Accept a full name with spaces

Write a single regular expression that accepts a full name pattern with minimum 3 letter characters and maximum 30 of them. In between the characters the user can have many spaces also. No numbers and no special characters are accepted. Letters can be either lower case or upper case.

Data that should be accepted:

1. Kostas Diakogiannis

2. Daniel Cipolla

3. Mauricio Cifuentes Navarro

But not!

Daniel23,

Kost@s

etc