The first piece from Whitlock's 'Four Extemporisations' is, you probably guessed, a homage to Frederick Delius. Marked 'Andantino, senza rigore' and quaver=74, it begins with a clarinet solo accompanied by Swell strings and 4' flute.
The chord stretches and frequent 'thumbing down' make the piece difficult. I think it would benefit from being arranged as a duet!
Whitlock was born with a bifurcated thumb on his right hand and the extra digit was removed while still a baby. The remaining thumb was longer and thinner than his left-hand thumb, being more like a middle finger which enabled him to use this digit for thumbing down and to play wide chordal stretches with a good legato. Much of the string writing requires this (or a large acoustic might help).
The harmony is delicious and not all Delius. There is a cuckoo call and some wonderful patches of Elgarian style. An orchestration would do great justice to the piece.