Blue Peter, Christopher Trace and Valerie Singleton are the first presenters I recall, somewhere along the line Trace left and the show acquired two more presenters, with some overlap between the first arrival and Trace's leaving. Those presenters were John Noakes and Peter Purves, I think it was Noakes who arrived first, his arrival announced after appearing in a swimming related article but I may have got those events confused. Back in the 60's, when this transition occurred, children's TV presenters were pretty much like their counterparts serving an adult audience, with maybe slightly informal dress, roll necks and monkey boots taking the place of collars, ties and shoes with a shine so perfect you could use them for a shaving mirror. The style of presentation was pretty much the same though, steady diction with clear pronunciation and a gently modulated tone, just like a normal person would speak to any other of the same, providing they'd benefited from elocution lessons or been brought up with received pronunciation, that is.
With the arrival of Noakes however something changed, I think it's fair to say that if you spoke to anyone in everyday life in the manner of Noakes presentation style, you'd find yourself in room with no windows, probably within the week. Yes, Noakes effected this style, where ever sentence was spoken in manner that inflected a vigorous portent, much in the manner of a music hall recitation or The Green Eye of the Little Yellow God. Time passed and Noakes's s style became something of a new standard for children's TV, the Saturday morning schedules became clogged with presenters acting as if they were having a fit. This state of affairs continued for some time and then David Belemy happened, Belemy bridged the gap between children's and adult's TV because he was featured in both. Unfortuantly for the sanity of the nation, he chose to adopt the Noakes manner in both contexts. Time Passed again, guess what happened, uh--yeah adult presenters are now also unnecessarily gesticulating twerps, presenting with a chaotically modulated speech pattern. I don't know any adults who can abide this trend, without the aid of a soporific, so the question is: Why---just bloody WHY?