Rapid development of the doctrine begun in the first years of the twentieth century, when financial loss, incurred as a result of frustrating event - sudden illness of King Edward VII in June of 1902 and subsequent cancellation of the coronation procession - brought in existence a line of ‘coronation cases’. Anticipating an event, spectators leased many rooms and bought seats in stands, along the route planned for the coronation procession. Moreover, some boats were hired for the purpose of viewing the naval review, which should take place same day with procession.
Per Megarry J in C H Giles & Co Ltd v Morris  1 All ER 960 at pp.969-970:
The reasons why the court is reluctant to decree specific performance of a contract for personal services (and I would regard it as a strong reluctance rather than a rule) are, I think, more complex and more firmly bottomed on human nature. If a singer contracts to sing, there could no doubt be proceedings for committal if, ordered to sing, the singer remained obstinately dumb. But if instead the singer sang flat, or sharp, or too fast, or too slowly, or too loudly, or too quietly, or resorted to a dozen of the manifestations of temperament traditionally associated with some singers, the threat of committal would reveal itself as a most unsatisfactory weapon; for who could say whether the imperfections of performance were natural or self-induced? To make an order with such possibilities of evasion would be vain; and so the order will not be made.…In general, no doubt, the inconvenience and mischief of decreeing specific performance of most of such contracts will greatly outweigh the advantages, and specific performance will be refused. But I do not think that it should be assumed that as soon as any element of personal service or continuous services can be discerned in a contract the court will, without more, refuse specific performance. Of course, a requirement for the continuous performance of services has the disadvantage that repeated breaches may engender repeated applications to the court for enforcement. But so may many injunctions; and the prospects of repetition, although an important consideration, ought not to be allowed to negative a right. As is so often the case in equity, the matter is one of the balance of advantage and disadvantage in relation to the particular obligations in question; and the fact that the balance will usually lie on one side does not turn this probability into a rule.
Per Lord Hoffmann in Co-operative Insurance Society Ltd v Argyll Stores (Holdings) Ltd  3 All ER 297 at p.301:
Specific performance is traditionally regarded in English law as an exceptional remedy, as opposed to the common law damages to which a successful plaintiff is entitled as of right. There may have been some element of later rationalisation of an untidier history, but by the nineteenth century it was orthodox doctrine that the power to decree specific performance was part of the discretionary jurisdiction of the Court of Chancery to do justice in cases in which the remedies available at common law were inadequate. This is the basis of the general principle that specific performance will not be ordered when damages are an adequate remedy.