Dogs come in all shapes and sizes - the UK Kennel Club recognises 221 different pedigree dogs, from Affenpinscher to Yorkshire Terrier (there are sadly no dog breeds starting with the letter ‘z’!).
Then there are all manner of crossbreeds, from so-called ‘designer dogs’ to lovable mongrels.
Each has its own list of positive and negative attributes, and it’s important to take plenty of time to think about what breed will fit into your lifestyle the best - for instance a smaller dog if you live in a flat, or a hypoallergenic dog if the mere mention of dog hair makes you think about sneezing.
There is even scientific research to guide you, in particular psychologist Stanley Coren’s groundbreaking book The Intelligence of Dogs.
And one thing you might like to consider is that some dogs are naturally better guard dogs than others.
Labrador Retrievers may be affectionate and popular, but they’re likely to welcome a burglar like a long lost friend - particularly if they come armed with a few tasty sausages.
On the other hand, other breeds are naturally suspicious of strangers, ever-vigilant and have the potential to be ferocious if challenged or confronted. It also helps if they look a bit scary.
Here are the 24 best and worst breeds of guard dog.
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13. Bullmastiff
Now we've reached the dogs you'd trust to keep your home and family safe. The mere sight of a Bull Mastiff should be enought to put an intruder off. They have a fearsome reputation which comes from their former job of guarding estates for 19th-century gamekeepers. When not on security patrol they are affectionate and chilled, although don't suit multi-pet households. They like being top dog too much. | Getty Images
14. Tibetan Mastiff
A lion would be a great animal to guard a house, but the authorities take a dim view of postmen being eaten. The next best thing is the luxuriantly-maned Tibetan Mastiff, with their distinctive thick coat designed for cold mountainous climates. Used to guard Tibetan temples in their native country, they will repel unwanted guests with extreme ferocity before cuddling up next to you on the couch. | Getty Images
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15. German Shepherd
When most people think of a guard dog they are probably picturing a German Shepherd - and for good reason. Popular with the army and police, if one of these dogs don't want you around, you'll quickly know about it. On the flip side, they are also very affectionate dogs who are great with kids. | Getty Images for Westminster Ken
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16. Australian Shepherd
An interesting fact about the Australian Shepherd is that it's not from Australia - having been originally bred in the USA. Wherever it's from, it makes a similarly good guard dog as its German counterpart. It was traditionally bred to herd and protect livestock from predators. That instinct is easily transferred to its home and human family. | Getty Images