Rear crew seat pins.
I don’t recall any rear seat pins. What I do recall is a Corporal Nav Inst getting his legs trapped under the table after accidentally inflating the Nav Plotters assist cushion. The Nav Plotters seat only went fore and aft whereas the outboard seats could swivel and the seat inflation was accompanied by the seat back tilting forward to push the occupants up and out of the seat.
As he was working on his own he was there for some time before anyone knew of his predicament. Don’t know how he was extricated but it probably involved a sharp knife into the offending cushion. As a by-the-way he never wore a watch and used to set the GPI 6 to 360 Knots and used the Miles and 10ths of a mile counter for the minutes and seconds for timing of whatever he was doing. Very clever I thought as a new Liney at Cottesmore in the late 60’s.