I don't think the lack of indicator will save you as you enter a box junction at your own risk if there isn't already a clear exit on the other side.
However, you should be in scope of the right turn exemption. You are allowed to enter a box junction for the purpose of turning right and wait behind another stationary vehicle which is also stopped while waiting to complete a right turn.
The legislation words it as follows:
"The prohibition in sub-paragraph (1) does not, in respect of a box junction within sub-paragraph (6)(a) of the definition of that expression, apply to a person who—
(a)causes a vehicle to enter the box junction for the purpose of turning right; and
(b)stops the vehicle within the box junction for so long as the vehicle is prevented from completing the right turn by an oncoming vehicle or other vehicle which is stationary whilst waiting to complete a right turn."