THE QUESTION ABOUT WHETHER SOMEONE HAS BEEN CONSTRUCTIVELY DISMISSED IS ONE THAT ARISES MORE AND MORE FREQUENTLY.
For those who want a very clear and definitive ruling on what constitutes constructive dismissal, one cannot do better than go to Lord Denning and we here do so, Quoting Lord Denning in Western Excavating (ECC) Ltd. V Sharp  1 CR 221 at 226:
“If the employer is guilty of conduct which is a significant breach going to the root of the contract of employment or which shows that the employer no longer intends to be bound by one or more of the essential terms of the contract, then the employee is entitled to treat himself as discharged from any further performance. If he does so then he terminates the contract by reason of the employer’s conduct. He is constructively dismissed. The employee is entitled in those circumstances to leave at the instant without giving any notice at all, or alternatively, he may give notice and say he is leaving at the end of the notice. But the conduct must, in either case be sufficiently serious to entitle him to leave at once. Moreover, he must make up his mind soon after the conduct of which he complains: for if he continues for any length of time without leaving, he will lose his right to treat himself as discharged. He will be regarded as having elected to affirm the contract.”