The first part takes the form of a play in which the cast portray contemporary amateur performers conceiving, creating and rehearsing the opera.

The format of the play altered radically in the early months of its existence, passing through at least three versions (including one specially written for radio) utilising different approaches to the exposition.

In this telling the long-term happy ending is revealed, that Juliet's uncle (the father of the visiting Crome children) took Sammy the rescued sweep-boy on as a gardener's boy.

The group of six adults (including the conductor) and six children choose this as the subject of their home-made opera, libretto by Anne Dougall, a young Scottish bank clerk, and music by Norman Chaffinch, an enthusiastic amateur.

Britten and Crozier had been thinking about a children's opera for some years, but only began to put the concept into practice in the autumn of 1948 when planning the programme for the second Aldeburgh Festival.

One afternoon Britten suggested two Songs of Innocence and of Experience by William Blake, entitled "The Chimney Sweeper", and as Crozier relates, "by that evening we had planned the structure, action and characters of a short opera in three scenes.

"[1] As with Albert Herring, the opera which had opened the first Aldeburgh Festival, the action was to be set locally in Suffolk, this time in Iken Hall, a large rambling farmhouse on the banks of the river Alde, the home of Margery Spring Rice.

Imogen Holst describes "a hubbub of excited comment" from the first audience as even seasoned opera-goers raised their eyebrows at the standard expected of the audience/chorus ("What!

"), and the consternation of a "tall thin music critic" uncertain of the precise divisi required for the four birdsong choirs in the "Night Song".

[2] While their mother is absent "seeing papa off to join his ship", the three Brook children of Iken Hall have been playing host to their three Crome cousins, together with their nursery-maid.

The first Audience Song is sung before the curtain rises to reveal the children's nursery at Iken Hall, which Rowan the nursery-maid is covering in dust-sheets in preparation for a visit from the chimney sweeps.

Jonny conceives the plan of smuggling Sam into his travelling-trunk so that he can be carried out of the house unseen when the Crome children leave the following day.

Everyone fusses around Juliet, who is eventually carried to her bedroom, as Jonny reassures Sam and urges him to "sit tight, and tomorrow you're a free man."

They pack Sammy into Jonny's trunk, with yet more food, only to run into a problem when it proves to be too heavy for Tom the coachman and Alfred the gardener to lift.

The extra manpower does the trick, and Juliet, Gay and Sophie watch from the window as it is loaded into the coach taking Jonny and the twins away.