It isn’t just the size of the egg that matters (Egg-stream Disinformation, Letters August 31). Freshness matters too.

I often have eggs which were laid the previous day. For a perfect soft-boiled egg, white fully set and yolk fully runny, they need 5 to 5½ minutes.

Breakfasting in Quito, Ecuador, some years ago, our friends served perfect 7-minute eggs because in Quito, altitude 10,000 feet, water boils at only 89°C.

Isn’t science wonderful?

Quentin Macdonald, Church Lane, Nether Poppleton, York