So it's basically like tailored investment advice, similar to an independent financial advisor?
Generally it's a bit more than that - yes you'll get financial advice but also say tax advice, estate planning etc... a mate of mine did his chartered tax advisor courses after uni at one of the big 4 accountancy firms then moved to a private bank.
Also you'll get a higher level of customer service - you'll not be going through a bunch of menu options to end up with some call centre in India but rather you'll be speaking to someone who knows you and doesn't need to read off a flow chart act like a robot etc... plug figures into a system and then say "computer says no" etc.. rather they can actually give advice on what is feasible and why etc..
Tailored financial products - for example regular banks have standard mortgages, loans etc.. the bloke that wants to use his fine wine collection or classic cars as collateral is going to draw a blank stare from Barry down at the Halifax.
If Lord Pontyby-Smythe wants to get a short term interest only mortgage to finance the rebuilding of some workers cottages and a new stable block on the estate and hopes to pay it pretty quickly once the sale of the London Mews house or his stake in one of the family businesses goes through next year but these things are tied up in different trusts etc..etc..* someone might need to advise on all sorts of convoluted arrangements various posh types have for maintaining their wealth. Often it isn't that they can't afford something but that they need some short term liquidity because most of their wealth is tied up somehow.... again Barry from the Halifax is going to be like "WTF???".
*just some waffly made up example that probably doesn't make sense... but just trying to make the point that the customers might have complex financial arrangements and need tailored products.