The 'Die Hards' at Bruce Castle?

Last night, Dan Snow tweeted a picture relating to the Middlesex Regiment, known as the Die Hards.

The Middlesex were the regiment of the British Army's first black officer, Walter Tull, who you can read about here.

Tony then tweeted me that he recalled seeing something about the connection between the Die Hards and Bruce Castle but he can't remember exactly what.

Any local historians out there who can tell us if Tony is correct?