From the 1st Armoured Division at Suez:
12th Lancers (armoured cars) and division artillery
2nd Armoured Brigade (60 Stuarts and 106 Crusaders)
The Royal Dragoons (armoured cars) from Syria
38th Indian Infantry Brigade (newly formed) from Egypt
150th Infantry Brigade from Cypress
50th Divsion Reconnaissance Battlion
(formerly the 4th Royal Northumberland Fusiliers)
The latter two units were in reserve, to be located at Maaten Baggush.
This is based on the account in Vol.III of the Official History.