Sorry Rojer Wilco, I respectfully disagree that everything hinges around what is written in the contract. Have a look at Re: Porter:
"The parties cannot create something which has every feature of a rooster, but call it a duck and insist that everyone else recognise it as a duck" 
Re Porter 
(1989) 34 IR 179 at p. 184 per Gray J
Its an oldie, but a goodie. Still good law and quoted quite a lot.
In addition to the express written terms, a contract may also subject to:
- pre-contractual representations and promises
- express oral terms and promises;
- implied terms;
- terms established through custom and practice;
- statute (i.e. the independent contractors act); and
- the common law.