Tidal rivers and the C&RT can be hazardous to your health.

It really all boils down to common sense and good practice, which don't enter into C&RT's actions or thinking in any shape or form, but do influence and drive the way a 'real' harbour authority's Vessel Traffic Services (VTS) radio operates and works to partly control, but mainly to assist and/or inform, those in charge of every one of the vessels underway, or about to get underway, in the area they cover. 

On busy commercial waterways vessel movements and the way the VTS works isn't entirely governed by hard and fast rules. The name 'Vessel Traffic Services' says it all really - they're there primarily to 'serve', in other words advise and assist, the masters of ALL the vessels moving about in their area, many of whom are engaged in a potentially dangerous game of waterborne dodgems with some big, lumbering stuff ranging from a few hundred tons displacement up to a few thousand.

Some of the answers to your questions are to be found in the mindset of the C&RT management in comparison with those in similar positions of authority at the likes of the PLA and Associated British Ports (ABP), who are the navigation and harbour authority for the Humber, the Trent up to Gainsborough, and the Ouse up to Goole. 

C&RT invariably demand that passage though the tidal locks they control is booked at least 24 hours in advance, . . . but to what end do they demand this - what purpose does it serve and why do they insist that boaters do this ?  We know that the C&RT/BWML staff at Limehouse don't make use of this time to pass on any of the navigational guidance and advice that the PLA have provided them with to ensure that the skippers and crews on the pleasure craft they'll be sending out onto the tideway next day know what to expect, and what is expected of them. Truth to tell C&RT just enjoy being officious by regimenting and ordering people about whenever an opportunity to do so arises, and that's probably why they lose all interest in pleasure craft that are escaping their clutches into another navigation/harbour authority's jurisdiction and don't bother to inform the London VTS about them.  

Above all, no harbour authority's VTS wants anyone cluttering up their already busy VHF working/listening channel by broadcasting information they don't want or need. Barring a mechanical breakdown or some sort of onboard accident, Magnetman and his small nippy motor cruiser are unlikely to be an impediment or a problem to any other river traffic, and as he's carrying VHF onboard he's able to contact the VTS, and all the other VHF equipped vessels in the vicinity, at any time if the need arises. On the other hand, a slow moving narrow canal boat without VHF and under the control of someone unfamiliar with the river and the standard practices and procedures that the regular commercial traffic will be following is highly likely to impede other, larger or faster vessels and to get into the sort of mess that Mr Stabby did on 10 August.