Thinking back to when all this happened there may be yet another local explanation in terms of an energy burst upsetting the DLM.
I live in the flight path of RAF Northolt and, at extended intervals, usually every 18 months to 2 years, they have a light aircraft flying at night, usually between midnight and three in the morning, repeatedly performing so called "Radar calibration" approach runs - or so I've been informed , for the benefit of the ground based radar ? (Cough ! Never used to happen 25 years ago) This was happening at the time I first lost the broadband speed in mid-October. So, if Northolt turned-up the wick/ changed the tuning of the ground-based stuff for the purposes of these tests or if the DSLAM or part of the distributed local network got a burst of the light -aircraft's microwave weather radar as it went over ?
No so far-fetched as it may seem, as I understand that even nocturnal atmospheric "Lift" conditions can cause MW transmissions to interfere with Broadband cable signals
I very much doubt that radar would bother VDSL, only over the horizon radar operates on HF bands, some secret squirrel stuff operates from Northolt, (this is not inside info). A black helicopter with lots of aerials was flying from there one night, no navigation lights and the downlink revealed that they were following a car. The MOD like many government bodies are not as clever as they think they are. Night time propagation on HF bands is a pretty well known phenomena. In the past I have operated high power on HF bands without my VDSL being affected.
I take on board what you say, but, I suspect that the sheer "Brute force" of some of these larger weather radars on big commercial aircraft, would break through any shielding and filtering and the have the potential to disrupt microprocessors and induce unwanted signals on circuitry in its proximal vicinity in the same way that military jamming does. Be interesting to know whether the area around Heathrow, especially Hounlsow, adjacent to the main landing runways (28R &L) is considered a a broadband and mobile fault blackspot.
It might be a future concern for me as extra commercial traffic might be going into Northolt - an operator at London City Airport obviously sensed a short-term commercial prospect at Northolt, before the development of of the third runway at Heathrow makes fixed wing operations at Northolt infeasible, and put in an application recently to operate out of Northolt in this interim period. That would involve a lot more traffic than the few civil air taxis, military and funny brigade transport that currently go in and out of there.
One other interference possibility I have considered is the presence of at least three mobile phone repeaters within 200 metres of my location, effectively triangulating my location. And, as I said in one of the previous posts, that some RFI is intermittently taking out the audio on my TV (Pictures OK). Probably the local taxi service TX, 300 m away but might be one of the trunked public service radio systems.
As fall-back against future broadband landline failures, I've just checked that I can get internet access through an old Nokia Windows PAYG phone by using it as a mobile hotspot - Cheap and cheerful potential fix.
With all the potential external sources you have mentioned such as water in ducts, radar, mobile repeater masts, taxi firms etc have you considered that those sources would potentially affect all users in the area and not just you and that there would be a substantial number of people reporting faults.
Have you checked with your neighbours to see if they also have a problem and if not it could be that the problem is more localised to either your own line or within your property.
I've been enjoying this entertainment thread, so much so I've got a bigger popcorn bucket!🤣
Over the last 30 years or so I have used laptops on radar sites, various two way radio sites and my office was under a tv transmitter with 1MW erp. Although interference is technically feasible I think you are looking too hard for a problem. My laptop spent a lot of time connected directly to transmitters, either via RS232 or ethernet cables. In all those years the thing never crashed or acted strange, the only time I ever had a PC hardware failure from RF was when a handheld radio sent a beacon while propped up against a CRT monitor.
Over a week since the BT/Openreach "Fix" and all seems to be well. The speeds have maintained. Noise margin has crept up a bit to 22.2/8.3.
Apart from a couple of re-boots, to add/remove other kit, SH2 has been kept on 24/7 - I suppose I have to wait the mandatory 10 (Or 14 ?) days since the last re-boot for the thing to fully re-train.
I don't fancy the chances of it keeping that way if the water in the shallow junction chamber that houses the cable spur to my place freezes - thus far , the lowest temperature at night has been 3C. In those circumstances we will find out whether OpenReach are pioneering a new form of "Untersee" cable - confirmed if they swap their Vans for "Unterseeboots" ?
Lets face it, if your household or cars electrics were immersed like that, they wouldn't stand a chance - fuses would blow ! What's more, the main 1930s/50s ex-Post Office cables in the street are probably only cloth, rubber and tar covered, with individual strands of the twisted pairs being possibly paper covered and I don't believe the air pressurisation system for main cables (Designed to keep water from penetrating cables) extends to these side road branches.
Agonising, yet again, but if OpenReach are intending, per the recent publicity, to extend Fibre to Premises (FTTP), then I would imagine they will have to install totally new fully tanked and waterproofed junction chambers and ducting, 'cause I can't see fibre optic strands, once penetrated by water, being as resilient as copper, especially in freezing conditions i.e. they'll snap.
As said before, if it goes down again, I've got an old 4G PAYG Nokia Windows phone which appears to be happy to provide internet to the PC over wi-fi or USB and an even more ancient TP-Link 3G dongle which is supposed to offer 7Mbps down when running under Windows 7 (But offered less than 1mbps even when running in compatibility mode under W10).
Going right off topic, I recently, pursuing some other information, just happened upon the availability maps for the French Telecom system Broadband and mobile internet system. If its to be believed, it seems most of the major towns are on fibre and getting 500Mbps down and 4G coverage is almost complete:-
Odd, cause ISP Preview says UK is No 5 in Europe whilst France is last:-
Hi, I am sure BT are more than aware of the state of the infrastructure. To an extent as a consumer it is not your problem unless it fails. Submarine cables traverse the oceans with repeater amplifiers at intervals too, probably a far harsher environment than South Harrow. Our pond pump is fully submerged and yet runs year in year out and is mains powered. Only time will tell whether your flooded cable box will survive, as you know the phone system is mostly DC and a small amount of leakage current can seriously increase corrosion, levels of current orders of magnitude lower than the average fuse would do serious damage in time. My own broadband has been up for over 9 days solid now, I think the speed is at the contractual limit, so I am ok.
Speeds of internet access around the globe vary a lot, but I am sure our older properties are an issue too. A friend who has moved to the US has symmetrical 1Gb/s upload/download, I am not sure I need that speed yet. The ISP review article perhaps seperates the technologies too much, does the end user care how the service is delivered? Coax, fibre, twisted pair or RF I doubt most people care.
Just to add a little to this tale. In our village at least one 300 metre run of BT duct is also used to carry sewage, there may be others.
My understanding is that submerged cables will deteriorate faster than ones running in air.