De Havilland had already studied the mounting of a 94mm/3.7 inch anti-aircraft gun in the Mosquito and, during December 1942, had already made detailled weight estimates for a ground-attack version with extra armour plating.

lapsus calami or it was really an anti-aircraft gun? I don’t think there was such heavy bomber owned or were designed by Nazi worth to shoot by this kind of caliber.

Just to answer one point with Four.
The Westland Whirlwind Designed in 1936 first flown November 1938 was the RAF’s FIRST twin engined SINGLE seat CANNON armed ALL METAL fighter.
And a further point when it first went into service at low level it could out fly and was faster than an ME109 ,an FW190 and a Spitfire flown by the average pilot.

Since no official record, I have to checked wiki
Westland_Whirlwind_(fighter)
and
De_Havilland_Mosquito
as we can see the Mosquito was faster than Whirlwind on normal speed.