UK visitor visa rules

These should be easy to answer but I can't find the answers on the Gov.Uk website.

If a friend of mine outside the EU receives a UK visitor visa, how long has she to use it within before it becomes invalid to use? For example, can she wait 9 months to use it to visit me in the UK, or does she have to use it within let's say 6 months?

Secondly, if she is doing a tour of several European cities. Can she, for example, fly from her home country to Paris or Rome and from Paris or Rome then fly to visit London using this visa? And after visiting the UK, fly back to Paris or Rome and from there to her home country (outside the EU)? Or does she have to fly directly to and from her home country to the UK (to buy a return ticket to the UK) to use the visitor visa?

She may use it prior to its expiry.

She may remain in the UK either up to six months or until her visa expires, whenever is sooner.

She may travel to and from the UK via a third country.

Thanks but that's not the question. Once she comes to the UK she has up to 6 months here, I know. But if she gets the visa in let's say March this year, and for personal reasons she decides not to use it for 12 months, is this permissable? Or does she have to come here to the UK and use the visa before a certain number of months are up, otherwise she has to re-apply for one?

Reread what Vinny said.

Each visa has an expiry date stamped on it. She can visit any time before the expiry date, but must leave the UK before the expiry date.

From the sources below, it appears that typically a visitor visa is issued for six months i.e. with the expiry date six months in the future. But it can be extended under certain circumstances.

Further reading

https://www.gov.uk/government/uploads/s ... _final.pdf

https://www.gov.uk/government/publicati ... eral-vat01

Ok thanks. I assumed there was some sort of fixed period she had to use it up within.