The following year, having established the problem stretched to thousands of elderly horses once used to transport British troops in the region during the First World War, she wrote to the Morning Post, which is now The Telegraph.

“They are all over twenty years of age by now, and to say that the majority of them have fallen on hard times is to express it very mildly,” she wrote.

“These old horses were, many of them, born and bred in the green fields of England – how many years since they have seen a field, heard a stream of water, or a kind word in English?”

Saying “many are blind – all are skeletons”, she told readers she was setting up a fund to buy the horses, restore any she could back to health and bring a “merciful end” for the rest.

She told them: “If those who truly love horses – who realise what it can mean to be very old, very hungry and thirsty, and very tired, in a country where hard, ceaseless work has to be done in great heat – will send contributions to help in giving a merciful end to our poor old war heroes, we shall be extremely grateful; and we venture to think that, in many ways, this may be as fitting (though unspectacular) part of a War Memorial as any other that could be devised.”

Newspaper readers sent the modern equivalent of £20,000, allowing Mrs Brooke to buy 5,000 ex-war horses. Most were “old, exhausted, and had to be humanely put down”, the charity said.

In 1934, she set up the Old War Horse Memorial Hospital in Cairo. Four years later, the charity put shade shelter and water troughs for animals in the city, and brought in its first motorised ambulance.

It now has four hospitals and 28 mobile vet units in Egypt, provides free care for around 160,000 injured and sick donkeys and horses, most of which are brought in by owners who cannot afford to treat them.