William's motto: "One should go to church and dine out" (3,4)

I believe the answer is:

ich dien

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'william's motto' is the definition.
I can't judge whether this definition defines the answer.

'one should go to church and dine out' is the wordplay.
'one' becomes 'i' (Roman numeral).
'should go to' says to put letters next to each other.
'church' becomes 'ch' (common abbreviation).
'and' is a charade indicator (letters next to each other).
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'dine' anagrammed gives 'dien'.
'i'+'ch'+'dien'='ICH DIEN'

Can you help me to learn more?

(Other definitions for ich dien that I've seen before include "Royal motto" , "Motto under the Prince of Wales's feathers (German)" , ""I serve"" , "(German) motto on the heraldic badge of the Prince of Wales" .)

I've seen this clue in The Independent.

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