For the Flanders & Swann fan, this collection is a must-have. It consists of 4CDs; the first is the original 1957 recording of At the Drop of a Hat, as it appeared on vinyl. It's very similar to, yet subtly different from, the 1959 "last night" recording of that show, which is the one that is generally available on CD and it contains a number of extras at the end, notably the superb and previously unreleased "Grandma".
"Hats around the world" is the second disc and contains various renditions recorded when they were touring. Some of these are of poor acoustical quality, but given that many of the tapes lay in a garage for 30 years it is remarkable that they have survived at all. There is much of local and historical interest - for example the number on the Sydney Opera House.
"And then we wrote" is the 3rd CD and this is a gem. This consists mainly of a 'retrospectif' programme recorded by the BBC in 1974, some months before Flanders died, and covers the full song-writing career of F&S, including the early days when they were writing for other performers. This contains some works of the highest quality, such as Guide to Britten, D'Oyly Cart and Pillar to Post.
Finally, the set includes a bonus disc "Hats off", a collection of 29 private recordings some, alas, of very poor quality but worth a listen if you are interested to see how the F&S style evolved.
In summary, this is a lovely collection of songs. With the exception of the first CD, there is remarkably little overlap with the wonderful (but inaccurately named) box set "The complete F&S"; "Hat trick" demonstrates not only the range of these wonderful entertainers but hints at what might have been possible had Michael Flanders lived long enough to complete the intended third show in the Hat series - provisionally entitled HAT TRICK!