Here's a description of the Custom's House according to The City Scene for Peterborough magazine (pp 4-5 of December 2011 issue):
The Custom's House
former Granary Town Bridge, River Embankment
Originally this early 17th century building topped by a cupola was a granary and owned by the Dean and Chapter of the Cathedral. It then became a Toll House for goods shipped up and down the River Nene and was later sold to Earl Fitzwilliam of Milton Hall.
Taxes and tolls were charged on goods that were brought in by barges and Fen lighters that travelled between Wisbech and Northampton. Goods shipped included wood and agricultural products like malt and corn from the fertile Fens. Even French prisoners were transported by river to Peterborough during the Napoleonic War and marched from the Custom’s House, used as a transfer station, to the camp at Norman Cross.
Church bells cast at William Penn’s foundry located near to where the Town Hall is today were also transported by barges. River traffic included passenger vessels or packets which did journeys three times a week from Peterborough to Wisbech. Apparently in 1810 our local poet John Clare used to make this journey regularly.
Over the years the railways took trade away from the river and in the late 1920s very little trade was done by river between Peterborough and Northampton with the exception of Fen lighters that traded up to Wansford for stone.
Before the improvements of the 1930s, the River Nene which was made navigable in 1713 was tidal up to Peterborough, but even so the tide only gave enough depth for the passage of loaded lighters on approximately five days in every fourteen. Those that did run had to be helped over the Northey gravel shoal between Peterborough and the Dog-in-a-Doublet by the release of water from Woodston and Orton staunches.
The Custom’s house is constructed mainly of rubble with dressed stone with the east end being constructed of brick. It has a Cooley Weston slate roof and a hexagonal cupola with a weathervane mounted above.
In 1888 planning permission was granted to convert the west end of the Custom’s House into a residential dwelling. The interior was converted to make three bedrooms on the first floor, with a sitting room, kitchen and back kitchen on the ground floor. No gas or water pipes existed at this time and heating was by coal fires.
Many long standing residents of Peterborough will recall that the Custom’s House was occupied by the Hammond family in the last century. They operated a boat hire business from the Custom’s House wharf and many a pleasant time was had by locals and visitors alike who chose to hire rowing boats for trips along the River Nene.
Since 1942 Peterborough Sea Cadets have used the building and they continue to do so – operating as T.S. Gildenburgh – under the present-day guidance of Major Andy Tannock R.M.R.
June & Vernon Bull – local historians and authors
I sometimes drove past this building, which is not really eye-catching as to attract one's attention, when my family gets a craving for KFC chicken, which is located along London Road near the football stadium of Peterborough Posh. Also, I've not been to nor near to the building but it would be interesting to do so.