In The Private Patient, the author - P D James - several times includes an assumption that "people of means" will have a permanent solicitor - a family solicitor - who knows their background and previous dealings, and can give a broad range of advice and information.
While this used to be the case - and is a useful means for fictional detectives to find out all about the victim's business - it is becoming less and less true these days. More likely, people choose their lawyer on a task-by-task basis, selecting him or her for particularly relevant skills or specialisation. This is understandable: "horses for courses", as the saying goes
In these times, how is one to choose a good lawyer, accountant, surveyor, etc? I suggest, by personal recommendation - from a family member, friend or other professional adviser (eg: ask your conveyancer to recommend a surveyor; ask your accountant to recommend a commercial lawyer)
Indeed, if you have used one lawyer who specialises in a particular field, they are likely to be ideally placed to recommend you to a lawyer for another type of work. Instead of the lawyer in a large firm feeling obliged to recommend you to colleagues in the same firm, a sole practitioner who specialises in one field, will have no reason to do other than recommend you to the best lawyer available for another type of work, whether they are part of a larger firm or another sole practitioner - as long as the referrer is confident of his or her own value to you in their specialist field
A word of warning: one area where this does not work well is where the referrer is paid by the referree: then they do have a vested interest and their recommendation, while it may still be good, is inevitably slightly tainted. Indeed, some estate agents require their staff to refer buyers and sellers to conveyancers that pay referral fees, whether or not that referral is in the best interests of the buyer or the seller or the transaction as a whole