In 1941 the Blenheim bomber was used to attack enemy shipping used to resupply the axis forces operating in north Africa. They would attack at masthead height incurring many losses. They did account for some 50,000 tons of enemy shipping sunk. Also used in photo reconnaisance work.

Air Force Homers - It's a little known fact but some Blenheims involved in photo reconnaisance carried homing pigeons which were used so as not to break radio silence & any emergency situation (being shot down). An English corporal was in charge of the loft situated on a low hill near Rabat. Eggs were regularly taken by local pigeon fanciers.

 

References:
Siege Malta 1940-43 - Ernli Bradford.