Ingredient

Bread flour

Milled from harder wheat with more protein than plain flour, so it forms a stronger gluten network and traps more gas. That is the whole reason a loaf made with it rises higher and chews rather than crumbles.

Sourcing
Sold as strong white bread flour in the UK. Look for the protein figure on the pack — 12% and up is what you want.
Varieties
Strong white, Strong wholemeal, Very strong (Canadian), Type 00
Quality cues
Should smell faintly sweet and nutty. A stale or musty smell means the wheat germ oils have turned, which shows up as a sour loaf.
Substitutions
Plain flour (expect a softer, lower loaf)
Storage
Airtight in a cool cupboard. Wholemeal versions contain the germ and go rancid far faster, so those belong in the freezer.
Shelf life
White 6-12 months; wholemeal 3 months, or a year frozen
Nutrition

Per 100 g

Calories
361 kcal
Protein
12 g
Fat
1.7 g
Carbs
72.5 g
Fibre
2.4 g
Sugars
0.3 g
Sodium
2 mg

From USDA FoodData Central (#168913). Raw, edible portion.