I worked on the Delta in '97 on the Brent Delta refurbishment, a flight up to the Shetlands the chopper ride out. It would be great to see how tall the hole structure was out of the water.
Got to say, I will probably regret not exploring one of these one day. As much as they always seemed pretty sparse of anything that interested me they are a bit of history I probably didn't fully appreciate back in 2017.