I'm afraid you're both wrong - and here's why.
Left turning lorries do not kill cyclists. Left turning lorries of a particular stripe kill cyclists, and, indeed, lorries of the same stripe run down cyclists from behind. And those lorries are construction traffic, primarily skip lorries. Cyclist deaths in London are not caused by the victims, they're caused by a particular type of driver, working for a particular type of company.
And the very good news is that the person who is taking on the role of Cycling Czar is an Architect, who knows that the way to get to this problem) but also via the JCT Contract. And that's what he intends to do - to get to grips with a particular problem that is causing the deaths of cyclists both experienced and inexperienced.
Just to say..........I started banging on about this to the LCC in 2007, and was told by Tom Bogdanovich that it was too complicated. Charlie Lloyd's LCC lorry campaign that followed focused on local authority vehicles which was a nice earner for the LCC, but did nothing to get to grips with construction traffic. It's taken this long to get the powers that be turn their attention to that which matters, and, so, it's time for three cheers!