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. 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?

Yes – UXO can still present a potential risk to construction and development projects in London.

The primary threat comes from German air-delivered bombs dropped during WWII that failed to detonate as intended. It is estimated that around 10% of munitions deployed across the UK did not function correctly. Although significant wartime and post-war bomb disposal operations were carried out, not all unexploded bombs (UXBs) were located or removed.

Ongoing discoveries of UXO during intrusive groundworks across the UK continue to demonstrate that buried wartime ordnance remains a potential risk – this is true across the country but especially in London because the level of bombing was so significant.

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

Before any intrusive groundworks begin, developers, principal contractors, and ground investigation teams should assess potential UXO risk through either:

This forms the first stage of an effective UXO risk mitigation strategy and should be undertaken as early as possible in the project lifecycle, in line with CIRIA C681 guidance.

Why does an early UXO Risk Assessment matter?

Where a credible risk is identified, appropriate mitigation measures should be implemented to reduce risk to As Low As Reasonably Practicable (ALARP).

Equally, unnecessary mitigation can create avoidable project costs, delays and operational disruption.

A professional UXO Risk Assessment will make sure:

Site-specific threats are properly identified.
Appropriate mitigation strategies are recommended.
Unnecessary mitigation measures are avoided.
Projects remain compliant, safe and commercially efficient.

Early-stage UXO Risk Assessments help developers make informed decisions, protect personnel, maintain compliance and avoid unnecessary expenditure.

If you are planning development or intrusive groundworks in London, obtaining a professional and unbiased UXO Risk Assessment should be your first step.

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.

1st Line Defence keep up-to-date with relevant and noteworthy UXO-related news stories reported across the UK, and you can browse through these articles using the buttons below.

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