If you hold debt in a UK Bank (and as we know now, banks own debt in each other in the UK and across Europe) you are going to be worried that this downgrade affects your own status.

The ratings agencies look at these banks first in the context of the strength of the likelihood of state support (and its nature) in the event of collapse (a realistic judgement), then as standalone banks, assuming NO state support (which is an academic exercise, really).

But what we are able to tell is exactly what is the effect of the state standing behind a bank - whether it is a bank where the state actually owns shares (such as RBS/NatWest) or not (like Barclays and HSBC). This is called systemic uplift.

Even though you may pretend as a bank that you are independent and do not rely on state support (like Barclays and HSBC continually assert) the commitment to save the entire system means you are actually dependent on the state for at least the size of your profits or, in crisis, for your very survival.

The recent Independent Commission on Banking, the Vickers report, addressed this issue in a less-reported aspect of its findings.

Based on Moody's August 2011 ratings, it came up with how many extra notches up each UK bank got as a result of the implicit state support and, indeed, the guarantee to UK depositors.

Vickers concluded that Lloyds/HBOS had 4 notches up, and RBS/NatWest had 5 notches up, to their ratings. These are actually massive in ratings terms, but that's obvious, because the state has a massive stake in them.

Your rating will affect the likelihood of international investors backing you with money and the rate at which you borrow and, consequently (for a bank), lend.

More interesting, though, was Vickers's reporting that Barclays has an uplift of 3(!) notches as a result of implicit state support. That's also massive in ratings terms. HSBC gets 2 support notches, according to Vickers.

So each of these banks, as a result of 2 and 3 upgrade notches is, firstly, more likely to be invested in internationally; and, secondly, pays less interest on its short and long term borrowing because of the UK state's support.

It has to be said that this benefit is clearly quantifiable - their profits have increased as a result. This is surely also taxable and should be taxed.

Bearing in mind both banks were able to offset losses from the last financial crash against their windfall profits resulting from being the fortunate survivors of it, they also had a further gain from state support of the system.

Last year Barclays Bank paid £213milllion corporation tax on its £12billion profits, and HSBC Bank paid £236million its £12billion profits. In both cases pretty minimal both in relation to their gross profits, and as a proportion of the total UK corporation tax take (about 1% together!).

So this is the context of today's ratings.

Moody's are now reflecting the reduced strength of the 'systemic uplift' to adjust downwards by one notch the overall ratings for Lloyds (from Aa3 down to A1) and a 2 notch downgrade for RBS/NatWest (from AA3 down to A2).

In other words, because the cushion is now much less plump, the bottom sitting on it is that much lower.

So Moody's now confirms that HSBC Bank plc has 2 uplift notches.

But it also now classes all three of Lloyds, RBS/NatWest and Barclays Bank PLC now as having 3 notches of systemic uplift.

So Barclays now receives as much benefit from state support as Lloyds and RBS!

Moody's overall rating of the UK government remains 'Aaa with a stable outlook'. Hmmm.

If the UK's overall ratings fell then so notionally does the quality of that state support, meaning the notches of uplift start to cancel out, because of the deterioration of the quality of the very cushion providing the uplift.

The question we have to ask is whether, to mix metaphors, with the increasing likelihood of the economic hurricane hitting us soon, we shouldn't actually be pulling the cushion from beneath the bottoms of the banks entirely?