I don’t think the ICAO interception procedure requires the interceptor to fly alongside the target. It merely needs to do a flypast.
Obviously this cannot work in IMC, so I guess the procedures were designed many decades ago for jet transports etc which mostly fly in VMC enroute.
Great story, CharlieRomeo Here, this issue (on instructional flights) is solved by turning off the transponder
They can fly closer in IMC as close as 100m but it’s hard to get a visual ident inside clouds or do ICAO interception as per the book, so you have to wait for VMC
I did read a story about a Robin that got stuck over tick clouds and he was escorted in an SRA cloudbreak toward some military base runway by two Rafales, I am not sure they maintained visual all the way?
Mililitary aircrafts can fly in formation in IMC down to x0m on proprietary DME-DME
Many years ago, returning to Inverness EGPE from the west coast, VFR below cloud covering the hills, I was approached by a Jaguar, circled twice, then it returned and circled again, before departing for good. I was in contact with ATC and squawking at the time. I didn’t encounter any wake turbulence.
A contact at the airbase said there was an event that day to allow desk officers to keep their currency on the aircraft.