when did duke of windsor return to england
In 1937.
Edward VIII

Letters Patent dated 27 May 1937 re-conferred the "title, style, or attribute of Royal Highness" upon the Duke, but specifically stated that "his wife and descendants, if any, shall not hold said title or attribute". Some British ministers advised that the reconfirmation was unnecessary since Edward had retained the style automatically, and further that Simpson would automatically obtain the rank of wife of a prince with the style "Her Royal Highness"; others maintained that he had lost all royal rank and should no longer carry any royal title or style as an abdicated king, and be referred to simply as "Mr Edward Windsor". On 14 April 1937, Attorney General Sir Donald Somervell submitted to Home Secretary Sir John Simon a memorandum summarising the views of Lord Advocate T. M. Cooper, Parliamentary Counsel Sir Granville Ram, and himself:

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Edward VIII [SEP] Duke of Windsor
On 12 December 1936, at the accession meeting of the Privy Council of the United Kingdom, George VI announced he was to make his brother the "Duke of Windsor" with the style of "Royal Highness". He wanted this to be the first act of his reign, although the formal documents were not signed until 8 March the following year. During the interim, Edward was universally known as the Duke of Windsor. George VI's decision to create Edward a royal duke ensured that he could neither stand for election to the British House of Commons nor speak on political subjects in the House of Lords.