Please note that some areas you need to visit might be closed from time to time for events. Hopefully all the info should be wheelchair accessible although the final cache unfortunately is not. GPS reception can be patchy in places but for all the stages I have tried to describe what you are looking for to make it easier.
You will walk just under a mile and it should take between 30-60 minutes to complete.
Stage 1 - N51 31.951 W000 07.518
In case your GPS won't settle you should be standing in Clarence Passage between 2 brick buildings. The southern one is the German Gymnasium and to the north is the Stanley Building, recognisable by external walkways on the front elevation. The German Gymnasium was constructed in 1864-5 for the purpose of providing facilities for the German form of gymnastics (I have no idea what they are!). It is now a restaurant serving German style food so you are now more likely to gain weight than lose it when you visit. The Stanley Building was built at the same time as the German Gymnasium by the Improved Industrial Dwellings Company. The company was a philanthropic response to the squalid conditions that many workers of the time lived in. The building contains many novel features for the time including self contained facilities for each flat and a communal playing area and drying space on the roof which were designed to improve the sanitation and health of the workers. On the south elevation of the Stanley Building you are looking for a white painted waste chute with a small sign on it which states that it's for "? AND ? ONLY". A = the total number of letters in the missing words.
Stage 2 - N51 32.110 W000 07.492
You are standing on the edge of Granary Square. However, where you see the fountains was originally a canal basin. Goods arrived by train from the north of the country to the Granary building (6 storey brick building which is now a university) where they were transferred onto canal barges and then taken on the Regent's Canal. If you look at the ground you can see the outline of where the basin was and also some writing in metal letters "Granary Basin 18B1".
Stage 3 - N51 32.096 W000 07.539
Now look to the south side of the square where you will see the Fish and Coal Building which was built is phases from 1851 to 1860. This is why it varies in height between two and three storeys. It was built to provide accommodation for the clerical staff needed to handle the paperwork generated by the incoming traffic of...you guessed it...fish and coal! Now have a look at the eastern end of the building and just above ground floor level you will see a blue sign with two words in white letters instructing you to do something if you were in a car. The number of letters in the first word is G whilst the number of letters in the second is H.
Stage 4 - N51 32.132 W000 07.535
Just a short walk across the square you should see a circular metal plaque in the ground. It shows how goods were transferred from the railway tracks onto canal barges by hydraulic crane, the outline of the base of this is still visible as well as the capstan. Look at the plaque. When was the "Hydraulically powered capstan" installed? 188C. Whilst you're at it when was the "Wagon turntable" installed? 185D.
Stage 5 - N51 32.228 W000 07.660
Again GPS reception can be very patchy due to the proximity of buildings close by. Luckily you can't get lost and miss the gasholder frames! The easiest way here is to walk by the canal on the towpath or at the upper level. You will see Gasholder No.8 (black painted) which has a park at its base and the Triplet Gasholders which are grey and within which flats have been built. Both sets of frames were moved here from the south side of the canal. The frames were dismantled and take piece by piece to Yorkshire to be repaired and repainted before being reassembled here. That was no small feat! Anyway, you are looking for something which is circular but a lot smaller. Just to the north of the park you should see a black painted metal wheel, about a metre off the ground (it is not attached to the gasholder frame). How many spokes does the wheel have? This answer is E.
Stage 6 - N51 32.154 W000 07.424
Nearly at the end now. GPS reception can be a little patchy here due to the roof. You should be standing under a canopy, just to the right of the entrance of a well known supermarket. This isn't the first time that this building has stored vegetables. It was originally a carriage shed and temporary passenger platform before the opening of King's Cross Station in 1852 before being converted to a covered potato market. The final clue is a painted letter on the wall, about 2 metres off the ground, behind the bike racks and just to right of a window (clue it's not O, it's below that and just to the left). Using the position of the letter in the alphabet convert it to a number (eg A=1 B=2 etc). This is answer F.
The cache is a short walk away and can be found at N51 F(Cx2).(E-6)AB W000 D(H+1).(G-1)(B-1)(A-1)
