The station opened deep in the winter of 1868, 5 years after the Underground network was begun. It served the District Line that was expanding East and West at the time. Originally it was 4 platforms, with a reversing siding between 2 & 3. The reversing siding has been filled in, it used to sit under the flat section of canopy roof in the photo below. Also in the photo below, on the left is the old Metropolitan Platform 1 with arched walls. On the right is the demolished Platform 4, Originally the Westbound District line platform. For many years it's been scaffolded to support a walkway above. The picture is looking East from the main building's roof. This was our way in, however, it has now been demolished and easily climbable scaffold removed.
After various debates about the route, with deep level 'technology' it was proposed a route would run at a deeper level below the District and Metropolitan line station here. A route was finally settled and the Brompton and Piccadilly Circus Railway deep level station opened, again in the Winter, this time in 1906. When the line opened it was generally known as the Piccadilly Line.

A new building was constructed adjoining the original District and Metropolitan Line station, it would house the lifts for the deep level Piccadilly station. It was designed like most of the Piccadilly line stations, by Leslie Green, featuring ox-blood red glazed brick frontage seen also at Oxford Circus, Down St, and Aldwych. The two Piccadilly line platforms were built on top of each other, with the Eastbound on top of the Westbound platform. The photo below shows the original access point to one of the lifts at the Eastbound platform, about 25m below the ground. A deep level District Line tunnel and part of a platform were constructed across from the Eastbound platform (possibly through the door on the right in the pic below), however it was never finished and the line didn't function.

90 degrees left from the pic above, and one can see out to the Eastbound Piccadilly line platforms. On the left is one former lift shaft, and the right the other lift shaft. The door in the mesh leading through to the other vent. Inside the vent was a large ventilation pipe to the surface building.

On the walls out to the platform were a few old posters. With the platforms just outside, I didn't loiter long enough to read the posters. Just pop the camera out and hit the shutter, then dive back into the shadows.

A few more worn posters on the opposing wall, we'd been spoilt by Euston's gems.

We then descended another 5m to the bottom of the lift shaft. Only to find...nothing, other than a locked Portacabin like room in the bottom of the shaft. The shaft is just on the right of the camera here, showing just how small this lift landing was, and how easily we could be spotted. Through the mesh can be seen the Westbound platform.

We then set about returning 30m up to the surface!

Safely back at the top, I grabbed a shot looking down the shaft we'd just ascended. The lights nearest the top of the photo are at the Eastbound level (25m), and the lights at the bottom next to Portacabin like room are the Westbound level (30m). You can see a bit of the original lift access shelf in the bottom right of the picture.

Looking across to the vents seen on the outside of the building at street level. This is where passengers would have walked into the lifts.

On the right is the original brick offices above the 1968 District and Metropolitan line Station. The glass roof giving light to the top of the stairs down to the District Line platforms.

As you can see in the photo above, it was getting light and close to service starting, so we had to get out of their sharpish. Thankfully we did so without issues. Props to Kev's rope skills.