Most insurers will not accept a new pet that is over eight years of age, although those already insured by then should have no problem in staying covered for the rest of their life. It is the age at which you start the insurance that is the problem.
There are, however, two companies who will offer insurance for any age: Marks & Spencer's, and Sainsbury's; These two have good track records for paying out too, unlike a few others, and none of them cut you off after a twelve month period.
So why insure an older pet if you haven't done so already? Principally older animals (humans included) tend to 'go wrong' more often the older they get. So your chance of needing veterinary attention increases. Veterinary treatment is getting cleverer too so we can now alleviate or operate on many more conditions successfully. But investigations and on-going treatment (anti-arthritic, heart….) can all add up to a pretty penny. Best if someone else pays?! Yes!
Insurance for older pets will, obviously be more per month than for a youngster, but given that you have a real risk of a big bill then you should find that you at least limit how much you will have to budget and still be able to afford the very best treatment on offer.
If you have been lucky enough to have had a healthy pet up until now, then be aware that at some stage things might change, and getting insurance before the event could really pay dividends. Please give it a thought!