I bow the knee to such extensive knowledge as is evident in all the above comments…but here we go anyway.

Say I was approached to “re-design” a historical garden, say it is from the Elizabethan Era and say it is very much in the public eye and visited by people from all over the world?

Where would one begin? Would you please the critics or would you draw a line between practicality, design and function? After all, most people who visit these historical houses and their gardens are out to be “visually entertained” for lack of a better term. I spoke to someone who visited such a property only yesterday and they described the garden as being “…overgrown and rather untidy…”
If you run the property as a business, which you must in the current economical climate, there is much to be said about keeping costs down and making sure it “looks pretty” in order to secure good visitor numbers and the resulting profits for the Trust.

It is a very fine line indeed and I take my hat off to anyone who tries their hand at it.

As you point out the main piece of evidence was the letter from Mercer Robert Laneham describing the Queen’s visit in 1575. Some of the written description, such as the quality of the gravel, was much more helpful than a painting or plan would have been, but in terms of proportion a plan would have been more helpful. As a mercer Laneham/Langham was very interested in measuring everything, and his detailed measurements were used in the recreation. I am tempted to wonder whether some of his measurements were to impress his fellow mercer correspondent Humphry Martin, leading to possibly oversized obelisks and a super-aviary. His spelling and use of words was sometimes ambiguous, with the fountain being potentially topped by a ball or a bowl (his word – ‘boll’. He says the obelisks were porphery, but EH used wood as the archaeological finds did not show enough physical support for porphery. More conjecture was used in the arbours, for which design a Du Cerceau engraving and a contemporary French garden arbour were used. The little fences seem the weakest part of the design, being both total conjecture and rather small. They should hopefully disappear when the hedges grow up through them, which will soften the whole look. Dr Keay’s presented approach was rigorous and wholely dedicated, and she and John Watkins’ team deserved to create a wonderful garden. The addition to the pot of more design-led conjecture may have created something less stark.

It is often frustrating that Local Authority Conservation Policy prevents any ‘conjectural restoration’ in listed gardens/building facades, and I hope that this use of both historical fact and educated guesswork by English Heritage itself will open the way to a more imaginative (ie creating an image or picture from several references) approach at the local level.