Perhaps not the best place to ask this question, but I couldn't think of any other place to ask and my normal resources on peerage address have failed me.
How did ranks/titles given by military service interact with peerage titles, specifically in Great Britain? The person I have primarily used to try and help myself figure this out is Horatio Nelson, but I cannot determine whether addressing him as "Admiral Lord Nelson" is a standard form of address or simply a loose, common way of referring to him and his accomplishments and something that would make the peers cringe. I also am aware that Nelson was given his peerage because of his Naval successes - would there be a difference for someone who had titles not through military accomplishments? Or would there be a difference dependent on branch of service- Navy versus Army? Or did it all come down to what their peer title was - a baron versus a viscount, for example?
Also, looking beyond just Great Britain, did it vary in different countries. or over time, for example during wartime or not? That might be making it too broad, but I've been struggling with this question for a while. Thank you in advance.
Formally it's military rank followed by the honorific or title, for example Admiral the Viscount Nelson, Field Marshal the Duke of Wellington or Marshal of the Royal Air Force the Viscount Trenchard. Informally these may be shortened to Lord Nelson, The Duke of Wellington or Lord Trenchard respectively. Indeed any ennobled person below the rank of Duke is known informally as Lord.
The three former Chiefs of the Defence Staff are life peers and so formally are known by the honorific "sir" which comes with each of them being a baronet, viz: Admiral Sir Michael Boyce, Air Chief Marshal Sir Jock Stirrup and General Sir David Richards. As members of the House of Lords, however, they may be known informally as Lord Boyce, Lord Stirrup and Lord Richards.
The final title of note is "the Honourable" which is used by the younger sons of a viscount and all sons of an earl or baron. Although rarely used outside of the most formal circumstances one might find something in the style of Captain the Honourable Rupert Badminton-Racket serving in the Household Cavalry.
Edit: source is Debrett's Correct Form.