In The Birmingham & District Cattle by-products Co Ltd v CIR [1919] 12TC92 all of the following were found to be preparatory activities (see the stated case at page 95):
Having got everything ready, the trade only commenced when the
company began to take in raw materials and turn out its product.
This principle is applicable to manufacturing in general.
Retail shops commence trading when they first open their
doors for business. This is referred to in J & R O’Kane
& Co v CIR [1922] 12TC303, at pages 341 - 342.