11.1 As discussed above,1 it is a general rule that a contracting party is entitled to decline to perform his obligations where the other party has failed to comply with a condition precedent to his liability or has substantially failed to perform an intermediate term of the contract. Four particular emanations of this rule are familiar in relation to the period covered by a marine insurance policy. An insurer does not become liable if the insured voyage is not begun;2 and, if it has begun, he is discharged from liability in the case of a change of destination (conventionally known as a change of voyage),3 deviation from the course of the contract voyage,4 or unreasonable delay in prosecuting the contract voyage.5 In summary, for the insurer to be liable, the contract voyage must be prosecuted in accordance with the contract and with reasonable expedition.6