Co trustee acting alone

[Hermitage]

Hi, I am a co trustee for a piece of land, 3 Trustees in total. 1 Trustee represents two thirds of the beneficiaries, The other 2, of which I am one, represent on third of the beneficiaries. The Trustees agreed to enter a land promotion agreement for the disposal of the land. One of the co Trustees has selected and appointed a solicitor without consulting his co Trustees, and requested the solicitor only take advice from him. I requested the lawyer take instruction from all three of us. He now says he cannot act for 2/3 Trustees due to conflict.

2 questions
can one co trustee appoint a solicitor unilaterally?
can that solicitor refuse to act for 2/3 Trustees? We are concerned that the interests of all the beneficiaries are not being protected.