"the message I am getting is that it is up to me to decide what work to target based on the firm's new strategy, and to go out and get it. I am obviously not a partner but I am a senior associate so the message is 'as a senior member of the team, we expect you to demonstrate partnerial behaviours and to go out and get the work and bring it in'. I am being told that I will be given 'support' to get this work (eg with business development initiatives) but it is up to me to identify lucrative targets and to bring them in."
Have you done this? Have you identified areas to target which are in line with the firm's strategy, and are you getting the promised support? What do you think is causing the 'you decide what work to target and go and get it' plan to fail?
The 'target it and go out and get it' message doesn't sound out-of-place in this context, to be honest. I should say at this point that DH has been a lawyer in the City for 18 years so I do have a reasonable understanding of the culture and how things work, and how it's different to a 'normal' work place.
Building a client base is easier if you have a specialism and can maximise it though. Are you struggling to do this because your area of specialism isn't something you can use in marketing to areas your firm wishes to specialise in? Marketing to a niche is more effective and if you can't do that you won't be as effective. Is there scope to adjust your area of specialism so it fits into the firm's strategy areas, or is it too different?
I think you might struggle to argue that you are redundant when your employer are perfectly happy to keep you employed and pay you a salary, and when going out and getting work is a key part of a senior associate's role. You're just struggling to do that. There might be good reasons for that, but that's the situation. And my understanding would be that in this type of situation, City law firms don't make redundancies. They gently push instead. Or sometimes less gently!
You say London rather than City so some of what I've said may not apply so much if not.
You could certainly have a conversation with a solicitor which would enable you to obviously give more detail than you are able to here, and context. Do you not know any employment lawyers yourself that you could just run it past? I assume not otherwise you wouldn't be asking, sorry!