Parliamentary elections

The majority of Westminster constituencies are wholly contained by a single local authority (and hence administered by a single returning officer/electoral services team). For example, 'Birmingham, Edgbaston' and 'Birmingham, Erdington' constituencies are completely inside Birmingham City Council. This makes things simple.

There are some Westminster constituencies which cover parts of more than one authority. For example, 'Carmarthen West and South Pembrokeshire' constituency covers part of Carmarthenshire Council and part of Pembrokeshire Council.

Usually in this situation, the relevant council will deal with booking/running the polling stations for the part of the constituency that falls inside their area, so we'd expect to get part of the data for 'Carmarthen West and South Pembrokeshire' constituency from Carmarthenshire Council (along with the data for 'Carmarthen East and Dinefwr' and Llanelli constituencies) and part of the data for 'Carmarthen West and South Pembrokeshire' constituency from Pembrokeshire Council (along with the data for 'Preseli Pembrokeshire' constituency). This is generally straightforward, but sometimes we need to deal with something non-standard:

• Problem: Sometimes a council will intentionally give us multiple files for their local authority: one for each constituency (or partial constituency). Solution: Merge them together into one file.
• Problem: Sometimes a council will accidentally give us a partial file because they've filtered the export to only cover only one constituency they administer (or part of a constituency). Solution: When we notice that we have less records than expected, contact the council for clarification.
• Problem: Sometimes when a constituency spans multiple council areas, one council or a shared services team will manage the data for the entire constituency, sometimes even including importing the addresses and polling stations from a next-door council into their EMS. This is rare, but it can lead to a situation where we've got one council sending us data for part of another council area or we've got a single file with data for more than one council in it. Solution: break the input files up by council area and store each bit in the relevant S3 bucket before importing.