Sorry, I couldn't find pricing data for that day. The closing price for Bitcoin (BTC) in terms of GBP on December 28, 2018 was 3,088.48. It was up 6.9% for the day.
DATE
OPEN
HIGH
LOW
CLOSE
December 28 2018
2,888.99
—
—
3,088.48
Daily pricing data for Bitcoin dates back to 7/14/2010, and may be incomplete.