The answer isn't just a big bill — but an uninvited guest.
Amongst the murmurings and clinking of crockery the guest, or more accurately, gatecrasher, walks towards the stage, thanks the master of ceremonies for offering her "such a kind introduction" and talks into the microphone.
Announcing to the room that she is pregnant earns her a round of applause. Further clapping ensues when she reveals that her unborn baby is a boy.
The uninvited guest has the audience of MPs and arms dealers on her side.
And then she informs the dinner guests that one million people in Britain have been forced to use a food bank in the last year. Their dinner, she reminds them, cost £246 per head.
"That's more money that someone receives on Jobseeker's Allowance in an entire month", says the uninvited guest.
The MC tries to silence her: "Will the sound guys turn off the sound please".
But she just shouts louder.
Her focus then shifts from food to the people profiting from the arms trade. This is after the UK arms industry's Annual Dinner at the London Hilton Hotel on Park Lane.
The ADS is the trade body for UK Aerospace, Defence, Security and Space industries and represents some of the 50 biggest arms companies in the world.
The uninvited guest is amongst many British MPs, civil servants and major arms companies.
"Get off the stage"
But she doesn't move. The uninvited guest tells the audience that she doesn't want her unborn child growing up in a world where people profit from weapons.
But she is drowned out by applause. She's not being congratulated; she's being hushed up. She is after all, uninvited.
And after reminding MPs how much money job seekers received from the government, she urges the MPs and civil servants to reconsider their own jobs.
The footage, which appeared on YouTube, ends with murmurs of ‘who was that?' and ‘no idea'.
The uninvited guest is in fact a member of the group, Campaign Against Arms Trade.
Andrew Smith from the pressure group said: "It's outrageous that the government actively supports and promotes this deadly trade."
"The fact that arms dealers were swilling champagne with over 40 MPs is a disgrace and shows the extent of the arms trade's connections and political lobbying".