Where to invest £300k

[WhatAWeekIHaveHad]

Shall I invest it into passive index funds?
I would not need the funds for 20-25 years (long term investment).

I can pay 1% for an advisor to manage it, but if I choose passive investments, is it necessary to do this?

A few things to think about before you decide where to invest

what is your risk tolerance and us that likely to change over time? Eg if you might be happy to risk a loss now but not at the time you need the funds, you will need to take account of this. Plenty of financial risk appetite questionnaires online

what is your tax status now and through the likely lifetime of the investment?

what investments do you currently hold? Do you have a pension?

what about diversification? All your eggs in one basket or do you prefer a spread?

What is the long term effect of charges?

once you can answer these questions, then you can choose the investment vehicle(s) and only then the funds

eg you might put an amount into emergency funds (typically 3-6 months of bills or income); then a mix of pensions (up to £60k per year can go in, subject to some rules, you get tax relief on the way in but pay tax on the pension when you take it, depending on current regulations at that time, and can’t take until 57. Then ISAs, stocks & shares perform better in the long term, up to £20k per tax year can go in, gains and income are currently tax free so if you think you might pay higher rate tax in retirement, taking extra income from ISAs can be helpful. Cash ISAs have the same tax treatment but typically lower returns over the long term

sorry, this is turning into a long response! This is quite a good guide to make a start, skip the steps that you already have in hand

Also, Martin Lewis has guides that clearly explain everything, and the forums are excellent too. https://www.moneysavingexpert.com/savings/investment-beginners/

you may ultimately decide to use an adviser but there are a lot of steps to work through first, and charges as high as 1% will eat away at your returns considerably over time

If you know you don't need the money for 20+ years then there is not much point in going through a financial adviser who will take a hefty commission. An IFA is a good idea if you need someone to go through your risk profile and determine how much it would be sensible for you to invest in equities versus lower risk investments. But with a 20-25 year horizon the chances of you losing money on a global or even US tracker are virtually zero (this has never happened in history since the great depression). So just put the money in a cheap global tracker and forget about it until 2045-2050.

There have been multiple crashes and significant downturns since the Great Depression, including the 2000 dot-com crash and the 2008 global financial crisis!

Yes, leaving it invested in a global tracker (passive index fund) for 20+ years absolutely helps mitigate against huge losses but it is not ‘practically zero’ risk as suggested above. @PollyPlumPeach has suggested even a US tracker won’t lose money yet since the Great Depression the S&P 500 (for example) has had negative annual results in approximately 33% of years since 1931. Please remember that recovery can take years too, hence the need for long term.

You don’t need a managed fund; a passive global index fund will be good and save you some fees. There’s no guarantee that managed have better returns than passive.