Catholics hoping to see Pope Benedict XVI at gatherings in London and Birmingham may bring sunblock, banners and torches - but not animals, candles or vuvuzelas. Other unwelcome items includes alcohol, gazebos, canopies and barbecues which are considered to be "things that...could pose a threat to yourself or others".
Flags, cushions and small folding chairs have been approved.
The instructions - on the official papal visit website - even detail that hampers and cool boxes should "not exceed 20in x 13in x8in (51cm x 33cm x 20cm)".
They advise people to bring "provision for all weather conditions", "medication as needed for the duration of your time away from home" as well as emergency contact numbers.
Also suggested is wet weather gear (rainwear) and "provision for sunny conditions (hats/caps, clothes to cover-up, sun cream)".
The advice includes: "Please be aware that the sun can burn even on a cloudy day. Please remember that overnight temperatures may drop significantly at this time of year."
Around 80,000 people are expected in Hyde Park, London, on September 18, with 65,000 in Birmingham's Cofton Park the following day.
They can expect sound levels of up to 96 decibels, according to the website, marginally louder than a lawnmower.
The beatification of Cardinal Henry Newman, a convert from the Church of England, at Cofton Park will be the "culmination" of the pope's four-day visit, said a papal spokesman.
The Pope will also meet with politicians including Nick Clegg and Harriet Harman, both of whom are married to Roman Catholics.
Pope Benedict XVI is also visiting Edinburgh and Glasgow during his four-day visit to the UK.