Shakespeare had already explored tragedy in his history plays, including Richard III, and in Titus Andronicus. The great series of tragedies, beginning with Hamlet, dates from four or five years later, and in many ways Romeo and Juliet does not belong with them. For a start, it is not a tragedy in the conventional sense because the fate of its protagonists is not a direct consequence of inherent characteristics or failings -whereas (for instance) Lear himself, through his own folly, initiates a chain reaction which leads to his downfall and death.

Romeo and Juliet, by contrast, are much more the victims of ill fortune than of their own vice or weakness, even if moralists may seek to suggest that the young lovers are punished for their intemperate lust or failure to obtain parental consent. This moralistic view is in any case certainly not Shakespeare's: in fact he lavishes upon his subjects extraordinary tenderness of language and feeling. They are 'star-crossed lovers' who ultimately bring good to Verona because their deaths shock their feuding families into reconciliation.

Shakespeare derived his play almost entirely from The Tragicall History of Romeus and Juliet, a poem by Arthur Brooke published in 1562. Brooke, in turn, found the story in a French version of an Italian tale whose origins go back at least to the mid-15th century. Brooke, who writes in clumsy couplets, is keen to stress the moral deficiencies of his hero and heroine - they are in thrall to 'unhonest desire', rely on 'superstitious friars' and thus are suitably punished - whereas Shakespeare, as we have already noted, is entirely in sympathy with his characters and derives much of his emotional effect from the acuteness of our identification with a couple who are romantically defiant, risking all for the sake of their love.

Romeo and Juliet is the play which, in English literature at least, effectively invented the modern love story. Its charm and its power derive from the romantic setting (Verona, an Italian Renaissance city), the youthful innocence and ardour of the lovers, and (perhaps crucially) the excitement and drama created by the opposition which they have to contend with, an opposition which does not simply stem from the older generation but which is starkly present in the feud between their two families and which seems to be supported by the malignity of Fate.

The richly realized context of their love is additionally enhanced by (for example) the superbly concrete character of Juliet's old Nurse, who fondly encourages the pair until the 'better' offer of Paris's love comes along. The Nurse's sentimentality and materialism are all too convincing, and are symptomatic of the way in which Shakespeare suggests that none of the other characters can match the lovers for sincerity and steadfastness, especially once the brilliant and impulsive Mercutio has gone.

Youthful as they are, we see that they are the people who grow and mature as the play progresses: Romeo, as sensitive and intelligent as the later Hamlet, realises that his 'love' for Rosaline is no such thing but merely infatuation: however instant the development of his love for Juliet may be, it is 'the real thing', as is Juliet's for him. The imagery of light and religion which Shakespeare consistently bestows upon the lovers is suggestive of the truth and value of their feelings: at the masked ball where they first meet, Romeo's immediate reaction to Juliet is that 'she doth teach the torches to burn bright', and their first words to each other are all built on the conceit that he is a 'pilgrim' and she a 'saint'.

The wit, tenderness, dramatic variety and poetic beauty of this play continue to work their spell: it has proved a perennial favourite inspiring, even in our century, works such as the musical West Side Story.