She's been the UK 3 times previously, holds a Frequent Visitor Card Immigration card for electronic/automatic entry into Hong Kong. Has a US Visa and 3 entry stamps, stamps for Singapore, Ecuador, Brazil, Argentina, Schengen and Croatia. I've supplied letters of garauntee, and also an official document from my government employer (not British government). Provided bank statements and proof of accomodation etc.
Her daughter has travelled with us several times to Hong Kong and Disneyland.

This all makes the visit visa dead easy, and the last two have been issued within 24 hours of application.