I wasn't really sure what to expect when we pulled open a manhole near the Holloway Road. My map showed it was being the High Storm Relief Sewer, as well as the North London Storm Relief. I'd been told that one of them was a 5ft RCP (Round Concrete Pipe), and uninteresting. Wanting to see for myself what was what, we quickly dropped down into an access shaft, with Adders.

The High Storm Relief Sewer (Camden Road Branch) is an overflow for the Fleet sewer. However after input from a well known drainor, Zero, in hindsight, we weren't in the High Storm Relief Sewer. However we did pass the 5ft pipe that was the High Storm Relief. No, what we were actually exploring, as we found out after the fact, was the High Level Sewer, basically an interceptor! Directly built by Sir Joseph Bazelgette's team in the middle 1800s. It starts on Holloway Rd from a local sewer, and eventually as it passes Gillespie Park, near Arsenal Football Ground, it becomes a fully fledged fast flowing deep Interceptor. The brown line on the map below highlights it's route, flowing left to right. It interacts with the Holloway Storm Relief, which dominates the drainage in this area. Whether it connects, or passes over/under the North London Storm Relief is a mystery still!

On entering the below chamber, the stench hit pretty hard, but it soon dissipated thankfully. The overflow path on the left in the pic below, was beautifully laden with small molehill like mounds of poop. A most pleasant scene to be greeted by. The chamber had the flow going from the foreground to the background, passing a small weir on it's way.

The overflow path on the left above, disappeared into the abyss below, down a 12m pit. GE035 bravely began to descend, only to find it caked in grease and fat. Far more disgusting than any poop. At the base of the ladder, is an opening into the Holloway Storm Relief.

The small weir here, looking upstream in the above chamber. The arched access room from the street is over the overflow weir on the left.

Initially I didn't think much more could be done in the drain/chamber. I put a pvc clad thigh into the flow, and it produced a number of small turds. I figured going by the colour it was likely an interceptor (which it turned out to be), and not a good idea to walk in. So Adders and I left.

After yet another disappointing look at the NE Storm Relief, which appears to have constant high flow in it. we opted to give the High Storm Relief another go. It being the early hours of the morning, we figured the flow should be minimal. I came back with Adders, and Ojay in tow, who was crashing on Adders's couch. The flow was only slightly less, but proved easy to walk in. First off Ojay seemed keen to descend the ladder to the Holloway Storm Relief. I had brought numerous bags with me to give extra protection. But Ojay was insistent on rolling up his bare arms, and setting off. Getting further than Adders, he reached half way, before giving up. On returning to the top, it was clear Ojay was going to make a great couch guest. His clothes peppered with splatters of poop and fat, his arm cut exposing blood trickling into the fat. I think I would have left at that point, but Ojay bravely/foolishly soldiered on.

We started off upstream, to see how far we could get. I already knew there were exit points up there, so it wouldn't be too traumatic. Just around the corner from the above chamber, we came to another overflow chamber and weir. It was a tiny version of the one we'd just been in. A small 4-5ft pipe came in at right angles to this tunnel, and between the two a pool. Adders put his whole leg carefully into it, and didn't feel the bottom. The water flowing in just past the overflow chamber was crystal clear, possibly a diverted stream/spring. I resisted having a sip. It would later transpire that this is the High level Storm Relief terminating.

We came to a side exit, which turned out to be the only exit that was usable. It had pipes running through it, which was something I'd not seen before. The usual wet wipes cling to the stairs, wet wipes being the nightmare for sewer companies along with fat.

Further up the stream, Adders backlights another small weir caused by debris build up.

Further upstream, and we came to an area with 3 larger pipes entering, as well as a ladder to a manhole in the middle of the road, which wasn't that useful! Looking carefully, you can see a grey layer about 10cms above the flow on the sides, this is a delightful mix of fat and grease.

One of the side pipes above, appeared to be a concrete lined older brick side pipe.

As I wandered up the passage, I found my torch hit something shiny at the top of the tunnel ahead. It was an abrupt end to the upstream journey. The pipe on the other side looked pretty small as well, so little more to see here (point 2 on the main map above). The others came up, and I pointed out the end of the pipe. We got back to the side exit, and I suggested we see the other end of the tunnel as we were here. All agreed, and we set off back to the initial large chamber.

The tunnel was long and straight for awhile, and we passed an exit point that was usable. Then another two side exit points that weren't. Normally I would have turned around, but I was intrigued by this largely unexplored pipe. The pipe twisted through an S shape section here.

Lots of calcium/mineral deposits draped the side walls, producing interesting and eery patterns. The ceiling kept rising as the tunnel grew heading downstream. At one point the roof flattened, and reinforcement beams could be seen. I wouldn't know until after, but we were passing the rail tracks around Drayton Park, and the East Coast Mainline.

Shortly after the above, I walked into a large chamber of uninteresting concrete walls. It's set up was similar to the chamber behind us. And overflow path to the left and a drop shaft. The mainline flowing from foreground to background. I would guess it links into the Holloway Storm Relief, somehow.

The protection barrier showing this had seen plenty of action, looking like how I imagine Tracey Emin's washing line to be.

This is looking upstream. In the corner above the overflow path, an inspection chamber. Disappointingly there were two exit points here, both in the middle of roads.

A great place to watch the flooding, the inspection room on the left. The downstream tunnel on the right. While the others lit up this chamber, I made myself scarce and headed off downstream. I was wondering why the tunnel was getting larger, and why I hadn't heard of this sewer before by the numerous explorers of yore. The drain map I had showed what I thought at the time was the High Storm Relief Sewer abruptly ending. After 100m, I realised that the flow was definitely deepening, and a groove had formed in the middle of the tunnel floor. I put my torch on full beam, and couldn't see any side exits ahead. Oh Bum! So I now faced the challenge of walking upstream in fairly heavy flow. I trudged upstream, and reached the previous concrete chamber, A bit out of breath and calves burning. I informed the others I couldn't see a way out, and that the flow was dodgy down there.

We were going to have to go against the flow, all the way back to the last usable exit. Bum! I rested briefly, and then marched off upstream. It seemed forever before we reached the first exit, and then the second unusable exit. We rested up for Adders, who was a more cautious drain walker. Giving him a few minutes to rest, we again plodded on to the exit. I didn't wait for the others, I just rushed up the ladder and popped my way to the street. Sitting on a low wall to get my breath. It's never fun to walk against the flow.

We'd completed the sewer, so after getting my breath back, I smiled with achievement. I looked again at the sewer map, and realised that there was an odd gap on the map, most likely due to the numerous train tracks that pass through here. I figured out that I'd actually been walking down the High Level Interceptor when I turned round, eek! This being point 3 on the above map.

After chats with Zero, and looking closer at the myriad of lines around Holloway Rd, it was obvious that the whole section walked that night was the High Level Sewer, not what we initially thought. While the element of mystery and investigation is fun with draining, walking down an interceptor is not! The tunnel would eventually drop into the Northern Outfall Sewer after Abbey Mills Pumping Station.

Thanks to Ojay and Adders.