A friend has this vine coming in from her neighbour's garden. It has extremely long spikes in between the leaves as you can see in picture 3 so very dangerous. Any idea what it is?

Maybe a Citrus.

Not a vine, but I agree with @Hortica - maybe C trifoliata.

Trifoliate orange (Citrus trifoliata)

Not trifoliate - leaves aren't 3-part.

Does a broken leaf smell like citrus? It looks like it could be a rootstock sucker.

agreed with above, and if your friend cuts it off, it won't grow back as terribly fast as a vine. (Or, if not cut, won't grow nearly as fast or long as a vine)

I suggest they try stuffing the branch back behind the fence .
Then it can continue to grow in the home of the owner.
It will not be a nuisance or danger to your friend.

What are the chances of it making a tasty fruit?

kniphofia said: Not a vine, but I agree with @Hortica - maybe C trifoliata.

Trifoliate orange (Citrus trifoliata)

Citrus trifoliata...used to be Poncirus trifoliata...the thorns are lethal.
Agree with other the trifoliate leaves rule it out.

Similar thorns but the leaves are not in threes. I had a lemon tree that had amazing thorns, but I don't know its name as it came up from root stock of a Mandarin Orange. It produced great lemons.

Could it be Bougainvillea?

purpleinopp said: Could it be Bougainvillea?

I don't think so. The stems appear to be flattened and the leaves have tiny serrations.

It really looks like a sucker from citrus rootstock or a water sprout. Too bad we can't see the base of the plant.

Looks a lot like Lisbon Lemon. It's sometimes used as a rootstock and suckers can be wickedly thorny.
There's a super-dwarf variety of Trifoliate Orange called 'Flying Dragon'. It's all stem and thorns. An impenetrable hedge to about 6'.

My father was always seeking a "boy-proof" hedge. Too bad he didn't know about Flying Dragon!

I think my root stock lemon must have been that Lisbon Lemon. It grew into a beautiful tree and made huge juicy lemons.

I have a flying dragon and you're right, its wicked. I'll look for a photo...

That was easier than I thought. Taken last month as the leaves changed color. Unlike any other citrus I know of they are deciduous.

My Flying Dragon doesn't get any fall color but I love the winter silhouette in the snow which outlines the wicked thorns nicely! Mine is about 8ft tall. It certainly is an effective barrier but trying to prune it to keep it from rubbing against the house is a painful and usually bloody task!

Thanks everyone. She tried crushing the leaves and smelling them and definitely a citrus of some kind. Now making sure the vine stays on the other side of the fence.

Except it's not a vine.