UXO Risk in London

UXO City Guide

Home Office Bombing Statistics for London

Record of German Ordnance dropped on the County Borough of London

High Explosive Bombs (All types)

46,062

Parachute Mines

752

Oil Bombs

1,941

Phosphorus Bombs

1,368

Fire Pots

238

Pilotless Aircraft (V-1)

2,417

Long-range Rocket Bombs (V-2)

518

Weapons Total

53,296

Why was London targeted and bombed in WWII?

Earlier in the war, London was targeted primarily for its substantial industry and infrastructure, vital to the UK’s wartime effort. Its sheer size meant that efforts to divert German bombers from strategic targets, often resulted in bombs being dropped haphazardly across the city.

One reference point that could not be disguised was the River Thames, which the bombers could follow to central London – and the city centre and areas along the Thames were heavily targeted.

From August 1940 to June 1941 alone, almost 15,000 high explosive bombs were dropped on London – a total greater than all of the UK’s other major cities combined¹.

Luftwaffe target photography of London (Isle of Dogs). Image credit: Imperial War Museum

Home Office Bombing Statistics for London

Details obtained from the official Home Office bombing statistics, indicates the quantity and type of bombs that fell on the most heavily bombed districts of London – please see the details used in the sidebar.

These statistics do not account for any bombs that fell unrecorded during raids, many of which fell into areas that had already been previously bombed and were potentially obscured by ruins and rubble.

They also do not include anti-aircraft shells; thousands were fired at attacking aircraft of which approximately 10% failed to explode as intended.

Destruction of Central London following the bombing raid of 29th-30th December 1940. Image credit: Imperial War Museum

St. Paul’s Cathedral, with destruction visible in the foreground. Image credit: Historic England

Major bombing raids in London

London sustained numerous raids throughout WWII and below are some dates highlighting the most devastating bombing attacks²:

15th September 1940 (the first major raid)
29th/30th December 1940 (the ‘Second Great Fire of London’)
19th/20th April 1941 (the ‘Thousand-ton raid’, the heaviest of the Blitz)
10/11 May 1941 (The Hardest Night)
June – July 1944 (the peak of the V-1 pilotless aircraft campaign)

Overall, approximately 80 major raids on London occurred during the height of the Blitz, though bombing would occur throughout the war. V-weapons (known as Vergeltungswaffen in German) were a particular set of long-range ’artillery’ weapons designed for strategic bombing during WWII, particularly strategic bombing and/or aerial bombing of cities, landed on the city as late as March 1945³.

The Hardest Night

The most devastating raid on London took place on the night of 10/11 May 1941. Burning buildings in Queen Victoria Street, EC4, after the last and heaviest major raid mounted on the night of 10-11 May 1941.

The moon was full and the Thames had a very low ebb tide. These two combined with a maximum effort by the Germans, before the moved east to attack the Soviet Union – to produce one of the most devastating raids on the capital.

It is impossible to provide comprehensive detail of the night’s many actions but a number of highlights include⁴:

571 sorties flown by German bombers – some crews flying two and even three missions.
711 tons of high explosive bombs (167 were recorded as unexploded the next day) and 86,173 incendiaries dropped.
London Fire Brigade recorded at least 2136 fires, 9 of ‘conflagration’ level, 8 ‘major’ outbreaks (rating over 30 pumps), 43 serious (up to 30 pumps), 280 medium (up to 10 pumps) and at least 1796 small.
Approx 1436 people killed and 1800 seriously injured.
The fires resulted in 700 acres of destruction – about double that of the Great Fire of London.
Final costs of damage in 1941 values – £20,000,000 – about double that of Great Fire.
Anti aircraft guns expended 4510 rounds – 2 bombers claimed destroyed.
Fighter Command in total dispatched 325 aircraft (not all over London). They claimed 28 enemy aircraft. One Hurricane was destroyed and another Hurricane and a Beaufighter were badly damaged.

A bomb-damaged Buckingham Palace. Image credit: Historic England

Bomb damage in London – April 1945. Image credit: Wikipedia Commons

As WWII progressed, German losses mounted and the Luftwaffe switched their strategy to night bombing in late 1940. This was safer for the bombers, but it reduced their accuracy considerably, so the tactic of ‘area bombing’ was often used instead⁵.

Large quantities of bombs were dropped over wide areas to cause damage and destruction in general, with devastating results to the entire Greater London area. On the night of the 29th– 30th December 1940, a strategic Luftwaffe raid saw many thousands of individual incendiary bombs dropped on London from large air-deployed containers – resulting in what was later called the ‘Second Great Fire of London’⁶.

Bomb disposal operations in Dalston – November 1941. Image credit: Historic England

An extract from the London County Council bomb damage maps, illustrating part of Holborn. Black indicates total destruction, purple indicates damage beyond repair, orange indicates blast damage; circles indicate V-weapon strikes.Image credit: The London Metropolitan Archives

Can UXO still pose a risk to construction projects in London?

The primary potential risk from UXO in London is from items of German air-delivered ordnance which failed to function as designed. Approximately 10% of munitions deployed during WWII failed to detonate, and whilst efforts were made during, and after the war to locate and make UXBs safe, not all items were discovered. This is evidenced by the regular, on-going discoveries of UXO during construction-related intrusive ground works not only in London, but across the UK.

Occasionally items of British explosive ordnance are also encountered – often associated with WWII defensive measures or troop operations. Anti-aircraft batteries were stationed across London, and collectively fired many thousands of AA shells. As with German bombs, some of these failed to detonate as intended and could pose a UXO contamination risk.

I am about to start a project in London, what should I do?

Developers and ground workers should consider this potential before intrusive works are planned, through either a Preliminary UXO Risk Assessment or Detailed UXO Risk Assessment. This is the first stage in our UXO risk mitigation strategy and should be undertaken as early in a project lifecycle as possible in accordance with CIRIA C681 guidelines

It is important that where a viable risk is identified, it is effectively and appropriately mitigated to reduce the risk to as low as reasonably practicable (ALARP). However, it is equally important that UXO risk mitigation measures are not implemented when they are not needed.

While there is certainly potential to encounter UXO during construction projects in London, it does not mean that UXO will pose a risk to all projects. Just because a site is located in London does not mean there is automatically a ‘high’ risk of encountering UXO. It really does depend on the specific location of the site being developed.

A well-researched UXO Risk Assessment will take into account location specific factors – was the actual site footprint affected by bombing, what damage was sustained, what was the site used for, how much would it have been accessed, what were the ground conditions present etc.

It should also consider what has happened post-war – how much development has occurred, to what depths have excavations taken place and so on. This will allow an assessment of the likelihood that UXO could have fallen on site, gone unnoticed and potentially still remain in situ.

Sources

^{1Richard Overy, ‘The Bombing War’ (London: Penguin, 2014)}
^{2Overy, Hale.}
^{3Lewis Blake, ‘Bolts from the Blue: S.E. London and Kent under V-2 Rocket Attack’ (Lewis Bake, 1990), 80.}
^{4RAF museum website}
^{5Overy, ‘The Bombing War’, 71-72.}
^{6Julian Hale, ‘The Blitz 1940-41: The Luftwaffe’s Biggest Strategic Bombing Campaign’ (Oxford: Osprey, 2023), 67.}

Recent UXO discoveries in London

Since the war, many items of UXO have been discovered across multiple cities within the UK, with London no exception. See the news articles below about UXO incidents and discoveries from national and local press in London.

Click on the following link to read news articles about UXO discoveries found across the UK in 2024.

UXO discoveries across the UK in 2024