An antique engraving by E. Scriven after F. Cruickshank.  Published by George Virtue, London, circa 1836-46 in  Henry Thomas Ryall's "Portraits of Eminent Conservatives & Statesmen with Genealogical & Historical Memoirs".   Henry Thomas Ryall (1811-1867) was an English line, stipple and mixed-method engraver and later used mixed mezzotint.  
Approx 18cms by 22.5cms.