The 10th arrived too late to play an active role in the action, primarily because Slade insisted on making a stirring, and apparently over-long, speech ending in the words: "... blood and slaughter, march!

Paget made no pretence of hiding his low opinion of Slade, once calling him "... that damned stupid fellow", in a voice that many nearby officers and troopers heard.

[citation needed] He was employed on the staff in England for six months, but returned to the Peninsula in August 1809 with a brigade of dragoons, and served there for four years.

[citation needed] On 11 June 1812, when he was under Rowland Hill in Estremadura, Slade was beaten by Charles Lallemand in a cavalry action at Maguilla.

"[13] Another officer wrote, commenting specifically on the Battle of Sabugal: “[General Slade] … let no possible opportunity for inaction to pass him - pretending not to comprehend orders, which the events passing before him would have made comprehensible to a trumpeter, … a curse to the cause, and a disgrace to the service.”[14] Sir Charles Oman expressed the view that he was capable only of following definite orders and lacked initiative.

[16] That Slade, accused of ineptitude by contemporaries, remained in command of a brigade until mid-1813 has been attributed by commentators to Wellington's widely perceived inability to rid himself of undesirable senior officers, except by employing various subterfuges.

[3] He died on 13 August 1859 at his home, Montys Court, and was buried at Norton Fitzwarren, near Taunton, Somerset, having been 'the oldest living member of the army save one'.

They had seven sons (six of whom joined the military) and two daughters:[4][21] Secondly, Sir John married Matilda Ellen Dawson, his late wife's sister, on 17 June 1822, (d. 12 September 1868).

[4] The National Portrait Gallery posits that one of Robert Dighton junior's military etchings in its Reference Collection was "probably" of Slade.