Operation Yellowhammer

Operation Yellowhammer is the codename used by the UK Treasury for cross-government "no-deal" contingency planning for the possibility that Brexit negotiations for the withdrawal from the European Union fail to reach an agreement or an extension by 29 March 2019.[1]

Should there fail to be a negotiated settlement by that date, the UK would leave the European Union, leaving a hiatus impacting on many aspects of the relationship between the UK and European Union. The areas affected would include money, citizens, trade, customs and a range of regulations.[2]

On 6 September 2018, a press photographer captured a snapshot of a "no-deal" planning document revealing some details of then-current preparations and the HM Treasury codename for those plans.[3] The document appeared to indicate the Civil Contingencies Secretariat, a department of the Cabinet Office responsible for emergency planning, had been used in anticipation of government policy.[4] No further details were revealed.

On 2 February 2019, a journalist of the London Times provided leaked documents about preparations by the Department for Transport using this codename. The documents are detailing command and control structures.[5]


  1. ^ "Operation Yellowhammer: Photo of secret government no-deal Brexit papers reveals questions over 'rail access to the EU". The Independent. 6 September 2018.
  2. ^ Morris, Chris (14 October 2017). "Brexit: What would 'no deal' look like?". BBC. Retrieved 6 September 2018.
  3. ^ Kuenssberg, Laura (6 September 2018). "Snatched pic gives insight into 'no deal' Brexit planning". Retrieved 6 September 2018.
  4. ^ Islam, Faisal. "It's been another first for Brexit". Sky. Retrieved 7 September 2018.
  5. ^ @SamCoatesTimes (2 February 2019). "37 page "Operation Yellowhammer" no deal planning pack for staff leaks. Marked "official sensitive"" (Tweet). Retrieved 2 February 2019 – via Twitter.