It seems odd to think that you'd adapt a successful television sitcom for radio, as with 'Dad's Army' and 'Steptoe and Son.' Particularly 'Dad's Army' which had so much visual comedy in it's television version. 'Hancock's Half-Hour' used the idea of Tony Hancock having a sort of 'stage personality' an 'alternative' persona. The pompous, lazy, 'actor' or 'comedian.' It didn't (one presumes) really reflect his 'real' persona. It wasn't until the writers, Galton and Simpson, were rejected by Hancock as writers when he moved to I.T.V. that the B.B.C. allowed them a free hand with creating several 30-minute comedy plays that the eventual series of 'Steptoe' was developed from one particular episode called 'The Offer.' Putting character actors into the main roles meant that there was room for more character-driven plots and far more believable situations than they could write for Hancock.
As for the 'Navy Lark,' there is a certain amount of what can only be described as 'slapstick' in this very amusing show. I know it sounds crazy to describe it in those terms, but having listened to it recently on BBC Radio 4 Extra, there is nearly always some sort of incident when the ship it's set on H.M.S. Troutbridge, ends up crashing into another ship or a harbour wall or something and there's a great deal of noise and commotion as a result. In fact, that's why so much radio comedy work better in some respects than television, the sound effects that are used. I know 'The Goons' can never be classed as a sitcom, more a string of sketches, but it must have been quite revolutionary in it's use of sound effects. Feet running, explosions, clangs, pianos falling, etc etc which are just completely nuts and very funny.
A favourite radio comedy of mine is 'Clare In The Community.' It's based on the comic strip which appears in the Guardian 'society' section. Clare is a social worker who manages to sort out other people's problems but can't deal with her own, more specifically, her relationships. There's a good mix of characters and it works well on radio. I just don't want it to move to television because it will lose it distinctive flavour. Imagining what the characters look like is one of the best reasons for any form of radio drama or comedy. It's a bit like reading a novel and imagining how the characters sound and look. It can be a real disappointment when there's a film or television adaptation of your favourite novel when you see how a particular character is cast and presented, it can be a real let down.
One of the best things about radio, again particularly with comedy but also with drama in general, is that it can really stretch actor's abilities. Thinking in particular with people like Kenneth Williams, who was one of the supporting actors in 'Hancock's Half-Hour.' He had an incredible voice range and could conjure up an almost endless parade of weird and wonderful characters to support Hancock, whether it be an annoying neighbour, policemen, doctors or whatever a particular story required. It's no wonder that Hancock became obsessed with how he was so 'up-staged' by not just Williams but by Sid James and as a result they didn't move to television with him in the early 1960's.