Eight boundary markers from a series originally established from 1868 onwards to delineate the Liberty of the Tower of London, a territory which historically enjoyed special administrative status distinct from the surrounding City of London and County of Middlesex.

The 22 surviving boundary markers overall are arranged in an irregular arc from Tower Stairs in the west to Tower Bridge in the east. Some 13 markers are identical in form: flat round-topped iron posts bearing the initials WD with the Pheon (broad arrow) symbol denoting Board of Ordnance ownership and their number in the sequence. These may belong to the set installed by the War Department in 1868, although some have since been relocated or renewed. The remaining markers vary widely in form and appearance and can only be dated approximately if at all.

The eight markers located within the City of London are as follows:

1: A square stone panel inscribed 'WD No.1. Boundary 12'0" West', set into the western wall of Tower Stairs. The notional termination point of the boundary line extends further west into what is now foreshore. This part of the wall was renewed when Tower Dock was filled in after the Second World War, and the marker presumably dates from this time.

2: A stone panel inscribed with the broad arrow and WD, at the base of a boundary wall to the east of Three Quays House. The lower part bearing its number in the sequence is below ground level. This marker probably corresponds with the 'stone in wall' recorded in the 1861 survey.

3: A painted iron post with rounded top, inscribed with broad arrow WD No.3, at the base of a boundary wall to the north of Three Quays House. Presumably renewed after 1967, when it is still recorded as being of stone.

4: A painted iron post with rounded top, inscribed with broad arrow WD No.4, at the base of a boundary wall to the north of Three Quays House. Possibly of 1868.

9: A square metal plaque with embossed inscription reading '9 TL BM', set into the road surface at the corner of Trinity Square and Muscovy Street. Date unknown, but probably mid-20th century.

11: A painted iron post with rounded top, inscribed with broad arrow WD No.11, at the base of a wall facing Trinity Square in front of Trinity House (Grade I). Possibly of 1868.

12: A painted iron post with rounded top, inscribed with broad arrow WD No.12, at the base of a wall facing Cooper's Row in front of Trinity House (Grade I). Possibly of 1868.

21: A painted iron post with rounded top, inscribed with broad arrow WD No.21, at the base of a wall to the London Metropolitan University building facing Minories. Possibly of 1868, renewed or relocated after wartime bombing.

Two surviving markers are excluded from this listing: #10, which was installed inside the Port of London Authority building (Grade II*) on its completion in 1922 and is already included in that listing, and #15, a commemorative plaque set up in 1992.

From the Middle Ages until the late 19th century, the Tower of London and its environs, referred to as the Tower Liberty or Liberties, enjoyed special administrative status. As a royal palace and garrison the Tower itself was a self-governing entity, distinct from the neighbouring City of London and County of Middlesex for purposes of taxation, law enforcement and military service. By the early 13th century at the latest, its prerogatives were extended to cover a strategically important buffer zone immediately beyond its outer walls, comprising Petty Wales to the west, Tower Hill to the north and what is now St Katherine's Way to the east. This area was intended to be kept free of buildings for defensive reasons, although encroachment proved inevitable as London expanded eastward. Disputes between the City and the Tower over their precise jurisdictional boundaries were common in the 16th century, prompting a legal judgment of 1536 describing the exact boundaries of the Liberty and the first mapping of those boundaries in Haiward and Gascoyne's survey of 1597. The Tower's sphere of influence reached its maximum extent in 1686 when additional parcels of royal land in Spitalfields, East Smithfield and Little Minories were added to its domain.

The Liberty declined in importance during the 19th century. The outlying areas were removed from its jurisdiction, its legal authority was gradually reduced before being merged into that of the County of London in 1894, and its subsumption into the London Borough of Stepney in 1900 removed its last administrative responsibilities. It maintained a ceremonial existence: in a procession still held every third Ascension Day, the choir of St Peter ad Vincula Church ceremonially beats the boundary, delineated by the marker posts. Bombing during the London Blitz and post-war road-widening led to the loss of many markers, although some were replaced or relocated. Of the original 31 boundary points, 22 remain marked.