During the study, which was published in the journal Obesity, healthy university students were fed a fat-laden diet including sausages, macaroni cheese and other food loaded with butter.

London - Hot buttered toast is right up there with a nice cup of tea for comfort and sustenance.

Sadly, making it often ends in frustration when your perfect slice falls apart as you try to spread on a cold lump of butter that just won’t melt.

Now designers believe they’ve conquered the problem by inventing a heated knife.

A button on the handle activates a battery-operated heating element that warms the blade to 41.8C (107.2F) – optimum for spreading butter, according to research.

Testers were able to butter a slice of toast perfectly within 30 seconds of turning on the knife.

The designers created it after a survey of 3,000 people found that butter not spreading properly was one of the biggest breakfast bugbears, alongside burnt toast and cold tea.

The poll found 1 per cent of those surveyed have resorted to heating butter with a hair dryer. Just over a quarter (28 per cent) use a microwave to soften it, 8 per cent put it on a plate on top of the toaster and 7 per cent heat a knife on the hob.

The researchers found the best spreading technique is to use the very end of the blade, scraping a layer from the surface of the butter, and performing short strokes starting in the middle of the toast to evenly cover the entire slice.

They found that 28 per cent of us use long strokes, while nearly half (40 per cent) use a combination of both.

Women appear to be more precise with their toast, with 70 per cent taking the time to spread butter right to the edges, compared with 60 per cent of men.

The knife was developed for the baker Warburtons, which has yet to set a date for production. ‘We’re thrilled with how well it works,’ said a spokesman. - Daily Mail