In practical terms, the phrases ‘commencement of development’ and ‘implementation of a planning permission’ will often mean the same thing, however, there are some key differences to be aware of, which can be very important. Firstly, it is important to note that both terms when used in legal drafting will usually have their own definition in the individual document. It is common when drafting legal agreements for both the terms to expressly exclude works such as site investigations, and erecting signage or boundary fences, which would otherwise fall within the definitions of ‘commencement of development’ or ‘implementation of planning permission’ commonly used in planning law. Section 106 agreements are often drafted in this way so that the planning obligations are not triggered by minor works and are conditional upon 'implementation' as defined in the agreement itself. In these circumstances, the effect of 'non-implementation' is that the planning obligations may not be triggered even though there has been commencement of development by, for example, demolition,