A construction contract that contained the following clause:

1. Any of the events which are stated to be a cause of delay is a Relevant Event; and

2. Completion of the Works or of any Section has been or is likely to be delayed thereby beyond the relevant Completion Date,

3. and provided that

(a) The Contractor has made reasonable and proper efforts to mitigate such delay; and

(b) Any delay caused by a Relevant Event which is concurrent with another delay for which the Contractor is responsible shall not be taken into account

then, save where these Conditions expressly provide otherwise, the Employer shall give an extension of time by fixing such later date as the Completion Date for the Works or Section as he then estimates to be fair and reasonable.

What are the implications of this clause to the contractor?