The Unilateral Declaration of Independence (UDI) by the Rhodesian Front government (under Prime Minister Ian Smith) in November 1965 placed Gibbs in a very difficult position.

However, Gibbs knew that the bulk of the officer corps, as well as the rank and file of the Rhodesian military, were solidly behind Smith's government and that such a move would lead to a coup d'état.

Gibbs announced that despite the UDI, he had no intention of resigning his office or leaving Rhodesia, and that therefore, he would remain in Government House in Salisbury as the sole legal representative of Queen Elizabeth II.

[5] With few exceptions, the international community continued to recognise him as the Queen's sole legitimate representative in the area—and thus, the only lawful authority in what London maintained was still the colony of Southern Rhodesia.

[8] However, his supporters set up a Governor's Fund to pay for the upkeep of the building, and with the assistance of a small staff, led by John Pestell, he managed to remain defiant.

[9] While Gibbs continued to occupy Government House, Dupont and his wife held official receptions at Governor's Lodge in the Salisbury suburb of Highlands.

Later he was appointed to Her Majesty's Most Honourable Privy Council and was made a Knight Grand Cross of the Royal Victorian Order (GCVO) by Queen Elizabeth II.