It was brewed in 1932 and made the newspapers:
"THE PRINCE SEES BEER MADE
Surprise Visit to East End Woman
The Prince of Wales spent over four hours in the East End of London.
The Prince began his tour by making a two hours visit to Messrs Charrington's brewery in Mile End Road, where he saw many of the processes of beer making.
He then drove to West Ham Town Hall, where he was received by the Mayor, Alderman Scolding. Afterwards the Mayor, Town Clerk, and the Prince set out on tour of West Ham.
The first call was at Park Place, a quiet little street off the busy Stratford main road. The Prince got out of his car, went over to one of the little old cottages, and knocked at the door. A woman opened it and the Prince said, "May I come in, please ?"
The woman drew back and the Prince entered, to see the occupier of the house, Mrs Livesey, sitting by the fire nursing her baby and washing her feet.
A Little Talk.
"Immediately I knew it was the Prince of Wales," Mrs Livesey told a reporter."I was never so surprised in all my life. I could do nothing, because I was washing my feet, so I asked the Prince if he would go upstairs. He went up and looked all over the upper floor. Then he came down and had a little talk with me."
After seeing the conditions in the old parts of West Ham, the Prince was taken to the council's Manor Road housing scheme.
"He was surprised by some of the things we showed him," the Mayor told a reporter. "The visit originated in a conversation I had with the Prince when we saw some boys in boxing competition in West Ham last year. He told me then that he wanted to see something of how our people lived. " At the end of his tour I asked him what he thought, and he replied, "'I have seen exactly what I wanted to see."""
Evening Telegraph - Wednesday 16 March 1932, page 9.
You can see from this map of the 1890's that Park Place was no more than an alley:
This aerial photo from 1952 gives an idea of what the area looked like. The corner next to Park Place has been demolished and replaced by some sort of yard:
Here are a few more details about the Prince at Charrington:
"PRINCE OF WALES BREWS BEER
MAY BE WORTH £60 A BOTTLE
SURPRISE VISIT TO HOMES
Beer which was brewed by the Prince of Wales during a visit London brewery will be Jealously guarded for over 30 years, and may be worth £60 a bottle.
The beer was brewed by the Prince when he paid an informal visit to Charringtons Brewery in Mile End Road. E. He consented to "mash" a special brew, and, watched by number of employees, operated the controls which started the "mashing."
This special brew will probably be put away mature for a long time. It will then be bottled, and some will be sent to the Prince. Other bottles will be distributed privately. The beer may become as famous the "King Beer" which was brewed by King Edward when he visited Burton-on-Trent in 1902, and some of which, when auctioned for charity, realised £60 a bottle."
Gloucester Citizen - Wednesday 16 March 1932, page 8.
£60 a bottle was a huge amount back in those days, when you could get a pint of Mild for 6d.
Now here's a bold claim:
"ONE OF THE STRONGEST EVER BREWED
The "Prince's ale "— brewed by the Prince of Wales when he visited Messrs. Charrington’s Brewery, Mile End Road, E., on March 15 - has turned out a great success.
It is classed one of the strongest beers ever brewed, and already has the smoothness characteristic of high-class English ales.
The brew is not for sale, and will be matured for at least another two years before any of it is available for privileged consumers.
So is the gravity that it is estimated that the duty will amount to £13 or £14 barrel."
Portsmouth Evening News - Friday 27 May 1932, page 11.
I felt obliged to work out the gravity based on the duty. In 1932, the duty on a standard barrel (36 Imperial gallons with an OG of 1055) was £6 14s. According to my calculations, duty of £13 a barrel would mean a gravity of 1107 and of £14 1115. So pretty damn strong. Though obviously not so much by modern standards, where beers can be over 20% ABV.
If they really let it mature for two years of more, the Prince of Wales would have almost been king by the time it was released. When his father died in 1936, he was briefly king before abdicating. Maybe that's why I've not heard of this beer.