Im asking on behalf of a friend , she has a 3yr old Bullmastiff and is bringing a Kitten home in 3 weeks time.

She has asked this question on a Bullmastiff facebook group but got mixed awnsers so i said i could ask here for her.

Her Diego is ok around cats hes never chased them ever as he was discouraged when he was a puppy and he either ignores them or wants to play.

She will be picking up a British Shorthair kitten in 3 weeks time she chose them as there known for there great temperments.

What woukd be your advice to her to have a successful introduction?

I know normally its advised to go cat then dog but she chose dog then cat.

If u google just that both blue cross and cats protection have u tube vids on the subject probably worth looking at for her.
I've done it vith cats to dogs and dogs to cats  and its been successful. Although current dog even at 10 doe need remind g not to chase the cats
Cats need to feel safe and often that having places up high to escape to and the dog needs to be kept under control probably on a lead to beginning with and separate room for cat if u arnt with the dog in a lead
Have alook at those videos

Some years ago I bought a dog gate which had a catflap/door in it.  Excellent for allowing cats to remain one side of the gate and the dog/s the other whilst they get used to each other.

There was a program on tv last night on 5Star called Cats and Dogs at war. Two very good trainers, Chirag Patel and Nanci Creedon, helped two couples who had problems with the dogs chasing the cats and how to defuse the situation. It can be found on catch up on channel 5

https://www-teamcatrescue-ca.cdn.ampproject.org/v/s/www.teamcatrescue.ca/amp/2015/11/04/introducing-dogs-and-cats-by-jackson-galaxy?amp_js_v=a6&amp_gsa=1&usqp=mq331AQHKAFQArABIA%3D%3D#aoh=16147248485394&csi=1&referrer=https%3A%2F%2Fwww.google.com&amp_tf=From%20%251%24s&ampshare=https%3A%2F%2Fwww.teamcatrescue.ca%2Fpost%2F2015%2F11%2F04%2Fintroducing-dogs-and-cats-by-jackson-galaxy
This guy is very good with cat things worth looking at and finding more of his things

I've always held the kitten for the first meeting and then closely supervised any interaction until I was sure that the kitten would come to no harm. I found it very useful to use a large dog cage (for my kitten) in the first couple of weeks, when I was busy and could not be around to keep a very close eye on proceedings. Worked very well because it allowed everyone to see each other and the kitten was safe.