There is meant to be a special tool for removing / fitting one type of the hose rupture valves, we tried to get hold of it the other year for a safety campaign on a BT but no such luck.
The valve had 6 holes on the face, stuck 2 x 4mm allen keys in opposite holes on the valve face then used a adjustable spanner on the allen keys to unscrew the valve.
The other type of valve was a normal internal allen key / hex fitting.
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