Dress for Dinner???

I have just discovered in our online "Cruise Personaliser" that P&O have now advised the different onboard dress codes for the ship during  the 6 week cruise on Oriana to Southampton ("Dress of the Day", as we used to call them in my Navy days). There will be 13 FORMAL , 9 SEMI-FORMAL and 19 CASUAL. Hope the first night we board in Brisbane isn't "Formal" 
 
The definitions of these are:

Formal
This is the opportunity for ladies to wear formal evening wear such as an evening dress, smart trouser suit or a cocktail dress. For men, a dinner jacket or tuxedo are the norm, otherwise a dark lounge/ business suit and tie or formal national dress is fine. (Applies to all ships.)   I understand that on P&O UK ships it is normal for 90% (or more) of men to wear tuxedos on Formal nights - and that the dress code applies right across the ship.
Semi-Formal
Ladies can wear anything from tailored trousers to smart separates or an elegant dress, while men are required to wear a smart shirt and trousers with a jacket such as a blazer or sports jacket. A suit and tie may be worn but is not compulsory. (From April 2009 Semi-Formal applies to Arcadia, Artemis, Aurora, Azura and Oriana only.)
Smart Casual
Stylish resort or leisurewear is ideal, for example casual separates or dresses for ladies and open-neck polo shirts and casual trousers (not shorts) for men. A jacket and smart trousers may be worn but are not compulsory. Smart dark denim may be worn however we request that the following items are not worn: sportswear, e.g. trainers, football shirts and tracksuits. Bring your brightest clothes for our Tropical evenings. (Applies to all ships.)