tenpence to the shilling

The British shilling was worth twelve pence, so tenpence would be a deficient exchange.

tenpence to the shilling

1. (UK, slang, dated) Mentally deficient.
   • 1909, Edward R. Hartley, Train Talks, page 4:

     I knew that chap; but he never was more nor tenpence to the shilling. He was one of the men, we say, who fell out of his cradle and knocked his head.

   • 1951, Crichton Porteous, Wild Acres, page 203:

     He felt no curiosity about news or daily events, and was getting to be looked on as 'tenpence to the shilling' in the head.

   • 2011, Ruth Hamilton, A Whisper To The Living:

     Whenever he did manage to engineer a meeting she always treated him as if he was only tenpence to the shilling, a few bricks short of a load, as if he needed another brain cell to qualify as a plant.