Today is the day many investors will have dreaded (not to mention the UK’s largest asset manager).

After 25 years Invesco Perpetual Income guru Neil Woodford announced he was leaving the asset manager to set up his own business. The alarm bells have started ringing for investors, advisers, discretionary fund manager, model portfolio managers, multi-managers and many more.

The most well-known asset manager in the UK is at the centre of all of their portfolios. Why? Because his High Income fund, which celebrated its 25^th anniversary in February, has returned an astonishing 1,906% since launch. No one can match him in the long-term performance stakes.

Woodford manages more than £25bn across his income range and investment trust and is very much his own investment brand. He has a reputation as a fund manager who can provide stability and reliability even in turbulent market conditions. Sounds good in today’s market doesn’t it? Yet amazingly he’s been getting stick for underperforming in recent times.

In 2012, Woodford was singled out in a government-commissioned report on the UK equity markets as the ideal fund manager and was appointed Commander of the Order of the British Empire (CBE) in the 2013 Birthday Honours for services to the economy.

You can see why everyone will miss him. All those fund selectors will be scratching their heads trying to figure out if they need to replace the ever-reliable Woodford-driven Invesco income franchise within their respective ranges.

Invesco also faces a massive headache; the media has constantly questioned the perceived over- reliance of the Henley-based asset manager on Woodford as the shining star in their business, though they also have one of the biggest and best fixed income teams in Paul Causer and Paul Read.

The fact is that with Woodford setting up his own asset management firm when he departs in April 2014, the benefits of the Woodford brand for Invesco in the last 25 years could quickly become negatives as flows could well follow him out of the door. Mark Barnett, the man tasked with replacing Woodford has a big job on his hands. Invesco has to put any investor fears to bed or face billions of pounds walking out the door and into Woodford’s new franchise – as well as other popular equity income funds – of which there are many.

A number of the large advice/execution-only firms in the UK have started to suspend the ratings on the cash-cow that is the Invesco Perpetual UK Income franchise. The bottom line is this is a massive blow for the UK’s largest asset manager.