One MP has billed it as "the biggest challenge between the Commons and the Lords".
But it's got nothing to do with Brexit - although you could argue that migration plays a part.
The traditional Lords vs Commons pigeon race started at Bletchley Park today, with 500 birds heading to Pontefract in West Yorkshire.
It's a contest that began decades ago - but the last event took place in 1928.
Now, MPs sponsor the birds to raise money for the Combat Stress charity.