Pinned straw:
One problem with that yield play idea @DrJP I assume you got the 4% yield from Commsec or a similar trading platform, as I just checked Commsec and they have ARGO (ARG) on a 4% yield, however that 4% yield is based on their share price, not based on their NTA, so the discount to NTA in the share price doesn't increase the yield.
It does mean that you are gaining exposure to their portfolio of mostly "blue chip" (larger) companies at a discount to what you would pay if you were to buy the same companies in the same proportions (to them) yourself, however if you're after income via yield, I'm not sure the Argo portfolio is the best way to go about it.
ARGO are so close to an ETF you could buy an ETF with a lower management fee than Argo charge and get similar yield that way.
Being a LIC (listed investment company) the benefits ARGO have over ETFs are (1) some discretion in what they hold, but they are a very plain vanilla large cap LIC, and (2) they use a profit reserve to fund their dividends, which means that they benefit both from receiving dividends from their investee companies and from their own trading, assuming they are generating profits from their trading. When they generate profits from trading, they pay tax on those profits and receive additional franking credits that they can distribute to their own shareholders in the form of fully franked dividends. The profit reserve allows LICs to hold back some of their profits to allow smoothing of dividends, whereas ETFs usually have to distribute ALL of their profits to unitholders after deducting their costs (including fees), like a trust generally has to (distribute all, not hold any back). So ETF income can be a bit lumpy compared to dividends from LICs like ARGO (ARG) and AFIC (AFI), but I'm personally not in any LICs at this point, or ETFs either, because I'm at a stage where I have the time to do my own research and pick my own exposures rather than outsource that to a LIC or ETF.
I've used them plenty over the years, just not right now.
Looking at their top 20 positions (below)...

12 of those are in the ASX20 Index:

The other 8 are currently all within the ASX50 Index except for two of them, being APE (Eagers) who are in the ASX200 and APA which Commsec says are in the ASX50 but they don't appear in the list, and I found them 2 companies below #50 (#50 being the ASX itself) so APA are currently Australia's 52nd largest listed company. Those other 6 - that are in the ASX50 but not the ASX20 are SUN @ #28, QBE @ #21, CPU @ #31, ORG @ #30, STO @ #26 and TNE @ #47.
So apart from APE (Eagers), the other 19 of ARGO's top 20 positions are all within the top 52 companies by market capitalisation on the ASX.
It's sometimes more instructive to look at what they do NOT hold, some examples from the ASX50 that ARGO do NOT hold as top 20 positions are highlighted in the red rectangles below:

Wisetech are down 25% in the past year, but ARGO have never held Wisetech, Pro Medicus, REA Group, Xero, Northern Star or Resmed as top 20 positions as far as I can remember, so ARGO have missed out on the phenomenal run that those companies have had while instead holding companies like Santos (STO) who are trading at the same levels they were 4 years ago.
Also since the reverse takeover of Sigma by Chemist Warehouse, Sigma (SIG) is now an ASX20 company (currently the ASX's 16th largest listed company) and they're not in ARGO's top 20, and SIG are up +118% in the past 12 months, keeping in mind that they weren't an ASX20 company 12 months ago, but it goes to show that ARGO:
Just my thoughts @DrJP for what it's worth.