Excavation of the well in Colchester Castle was undertaken by the North East Essex Sub-Aqua Club under the direction of Stuart R. Bacon, on three separate days. The investigations aimed to find out if there was a cistern underneath the well and to discover any evidence of Roman work. No evidence for a false bottom to the well was recovered.<1>

A watching brief was held during the excavation of a hole for the insertion of a replacement drain. The excavated hole was of disturbed material remaining from the insertion of an earlier brick lined drain in the 1930's.<2>

A watching brief was held during work as part of phase II of the restoration of the castle. The work included the replacement of the 1930's wooden steps situated against the east wall. Five holes were excavated by hand in preparation for concrete footings of the new steps. Four of the holes were 40cm square and 1m deep. One was 1.5m x 1.1m and 0.5m deep. No features of archaeological significance other than the footings of the Castle were noted. There were some residual finds.<3>

During the period between 1931 and 1933, Dr. P.G. Laver made several investigations into the Castle Keep. In 1931 a north-south section was cut 'with great difficulty' in the small prison. It was made through a limited gap in the Norman tile floor.<4> The exact dimensions of this excavation are unknown. In 1932 Trenches cut by Laver <5> included one at right angles to the east wall of the keep, immediately south of the existing doorway. This revealed a drain-pipe and robbing of the Roman work. Two other trenches were cut up to the west face of the remaining Norman partition wall and revealed the temple podium and in 1933 a long east-west section was excavated through the sub-crypt 'small prison'. Again the dimensions of this excavation are unknown.<6>

Excavation of the castle chapel ahead of the construction of a new building purposefully built to house the remains. The chapel project was sponsored by the builders merchants Kent Blaxill to celebrate 150 years of trading in Colchester.<7> After removal of the 19th century roof, the floor of the chapel was cleaned and recorded in detail. Nothing of the original floor surface appeared to have survived.<8>

Investigations were carried out of the remains of the temple podium and overlying deposits beneath Colchester Castle, ahead of the insertion of a lift shaft. An area of 2.4 x 2.3m was exposed revealing the podium at a depth of 3.15m from the castle floor. No features of Norman or later medieval date were observed. The total area examined covered 3 x 2.5m and also revealed post medieval stone robbing activities as well as post holes and a trench attributable to the time of Charles Grey's ownership.<9>

Excavation of Colchester Castle well house. No report. Part of Colchester Castle Post Excavation programme (pers comm. Carl Crossan 27/01/2000).<10>

In March 1977, the reconstruction of the floor of the sub-crypt ('small prison'), prior to its fitting out as a display area, offered an opportunity to obtain control data against which Laver's 1933 excavations (see ECC814) could be assessed. It also afforded the possibility of obtaining some dating evidence from some of the strata, since Laver collected no pottery here. A six metre length of Laver's trench was emptied and two adjacent areas within the apse were excavated to provide dating evidence. The principal result was to provide additional data on the tile raft.<11>

A number of burials (MCC9291) have been found near the entrance to the Castle, lying over the ruins of the chapel, barbican and forebuilding, themselves sealed by demolition rubble of 1683.<16> Drury suggests they relate to the use of the keep as a prison during the late 16 and 17th century (until 1633).

Engraving print of castle, looking north from the area of the current park gates, the 1824 picture shows a house to the west and barn to the east of the castle (these are now demolished).<12>

Oil painting of Colchester Castle, looking North West.<13>

A map made in 1622 shows a survey of the castle lands, the property of Lord Stanhope. The map shows houses in Maidenburgh Street & East Hill, as well as the castle and the White Friars Gatehouse.<14>

The archaeological evidence is summarised in the 2013 Archaeological Assessment.<15>

In 2016, Peter Berridge argued that the Castle was only ever two storeys high, contra the standard theory of three storeys.<16>