It's often assumed that Lenin and Trotsky were the major figures who decided the fate of Nicholas and his family, but it's quite clear from the records of the Petrograd Soviet in the days immediately following his abdication, that, even if the Bolsheviks had not seized power, Nicholas would have been lucky to escape the same fate. For example:
THE EXECUTIVE COMMITTEE OF THE PETROGRAD SOVIET DEMANDS THE ARREST OF THE ROMANOVS
[Session March 3, 1917]
RESOLVED
1) To inform the Worker Deputies that the Executive Committee of the Soviet of Workers and Soldiers Deputies has resolved to arrest the Romanov family and to propose to the Provisional Government that it carry out this arrest conjointly with the Soviet of Workers' Deputies. In the event of a refusal, to inquire what the attitude of the Provisional Government would be, should the Executive Committee carry out the arrest.
Then a few days later, when Nicholas is under virtual house arrest at Tsarskoe Selo
Minutes or the PetroGrad Soviet Executive Committee Session of March 9 Concerning the Disposition of the Imperial Family
1. ON THE ARREST OF NICHOLAS ROMANOV.
In view of the information that the Provisional Government has decided to permit Nicholas Romanov to depart for England, and that he is at present on his way to Petrograd, the Executive Committee has decided to adopt extraordinary measures, immediately, for his detention and arrest. An order has born issued for occupying all the railway stations by our troops, and commissars [vested] with extraordinary powers have been dispatched to the stations of Tsarskoe Selo, Tosno. and Zvanka. In addition, it was decided to send radiotelegrams to all towns with instructions to arrest Nicholas Romanov and, in general, to adopt a series of extraordinary measures. At the same time, it was decided to inform the Provisional Government at once of the unswerving determination of the Executive Committee not to permit the departure of Nicholas Romanov for England, and to arrest him. The Trubetskoi Bastion of the Peter and Paul Fortress was decided upon as the place of confinement for Nicholas Romanov, and its commanding personnel was changed for this purpose. It was decided to carry out the arrest of Nicholas Romanov al all costs, even if severance of relations with the Provisional Government is threatened.
Nicholas never did go to England. I have put some of the background why at
http://www.royal-betrayal.uk/
