Further to my last post I have talked to people who flew all the Trident marks ( I only worked the 2 and 3 ) and yes its true that the main landing gear could be used as a speed brake , there was a switch near the gear lever to isolate the nose gear the main gear was then dropped in the normal way and you would get TWO greens when it was down and locked.
I can only wonder at how meny people came close to landing with the nose gear up !.
To make matters worse this option was only fitted to the Trident 1E.
I hope this answers the question fully.