speeding ticket while driving on a American Licence in the UK what will happen

Apparently, they can enforce an on-the-spot fine if the driver doesn't have a UK address.  http://www.direct.gov.uk/en/Nl1/Newsroom/DG_177085  It looks like this was changed with foreign HGV drivers in mind, but presumably it would apply to drivers of rental cars too.

Unless things have changed since l was an officer (and they may have,it was 10 yrs ago !) police don't issue on the spot fines for traffic offences,they give fixed penalty notices,which don't have to be paid on the spot.

Police also have the power to arrest a driver under s25 of the Police & Criminal Evidence Act,if they're not satisfied with the name and/or address given,or that it can't be verified,or it's not suitable for the service of a summons,such as in a foreign address. l don't think the power is used often,at least not in the case of foreign drivers,but it's there if necessary   

Apparently, they can enforce an on-the-spot fine if the driver doesn't have a UK address.  http://www.direct.gov.uk/en/Nl1/Newsroom/DG_177085  It looks like this was changed with foreign HGV drivers in mind, but presumably it would apply to drivers of rental cars too.

Unless things have changed since l was an officer (and they may have,it was 10 yrs ago !) police don't issue on the spot fines for traffic offences,they give fixed penalty notices,which don't have to be paid on the spot.

Well, you'll note that the Press Release that I linked to in my post is dated 1 April, 2009, so (unless it is an April Fool's Joke from DirectGov) it certainly does look like things have changed in the last ten years!!

Well, you'll note that the Press Release that I linked to in my post is dated 1 April, 2009, so (unless it is an April Fool's Joke from DirectGov) it certainly does look like things have changed in the last ten years!!

Yes l saw the link and No,l don't believe they have changed. I think you're confused about what an "on the spot" fine is..it doesn't mean that you have to hand over payment there and then at the roadside...Police do not take cash at the roadside..and never have. The term just means that you get a ticket at the roadside,which you can send in payment for,as opposed to having to go to court. So maybe the April Fool's joke is on you !

http://www.homeoffice.gov.uk/police/powers/road-traffic/

What’s a fixed penalty notice (FPN)?
If you’ve committed a minor traffic offence, like not wearing a seatbelt or driving with a broken headlight, the police may issue you with a one-off fine called a fixed penalty notice.

Non-endorsable offences - meaning those which don’t result in points on your licence  - usually incur a fine of £30.

Fines for endorsable offences like speeding are usually £60, although there may be some exceptions. More serious offences such as driving without insurance can incur fines of up to £200.

Police do not have the power to make you pay fines on the spot.

If you feel a penalty notice is unjust, you can choose not to pay the fine and argue your case in court. If you do pay the fine, you won’t be prosecuted and no record of your offence will be kept.

Recipients have 28 days to pay the fixed penalty or request a hearing otherwise the fine will increase by 50%. You’ll be reported for prosecution if you fail to pay a fixed penalty for an offence detected by an automatic camera within 28 days.
   

Maybe you are right but quoting from the press release;

"The Police and examiners from the Vehicle Operator and Services Agency (VOSA) can now collect on-the-spot payments from alleged offenders who cannot provide a satisfactory UK address."

Maybe you are right but quoting from the press release;

"The Police and examiners from the Vehicle Operator and Services Agency (VOSA) can now collect on-the-spot payments from alleged offenders who cannot provide a satisfactory UK address."

http://www.timesonline.co.uk/tol/news/uk/crime/article5854132.ece

March 6, 2009
Foreign drivers face £900 roadside fines to halt rise in crashes


Foreign drivers will have to pay on-the-spot fines of up to £900 for flouting traffic laws under new legislation to be introduced next month.

If they do not have enough cash or a working credit card their vehicles will be clamped until they pay — and they will face an additional £80 release fee.

The law will also apply to British residents who cannot prove at the roadside that they have a valid address in Britain.

The fines will be described officially as “deposits” when introduced on April 1 because the money would be refunded if the driver went to court and was found not guilty. In practice, very few foreign drivers are likely to return to Britain to contest their cases.

SNIP

Recent spot checks at Holyhead, in Anglesey, found that three quarters of lorries that failed safety tests were registered overseas.

Inspectors from the Vehicle and Operator Services Agency, which enforces lorry safety rules, will have the same powers as police to demand payment of deposits and to clamp the vehicles of non-payers. Drivers observed committing more than one offence will pay a maximum of £900 at the roadside.

The standard deposit for a careless driving offence — including driving too close to the vehicle in front or reading a map at the wheel — will be £300. Deposits for speeding offences and using hand-held mobile phones will be £60, in line with existing fixed penalties.

I assume that those in hire cars will have the clamping fine and any additional costs to the hire company, deducted from the credit card they used to hire the car.

Some more on roadside fines, from police sites:-

http://www.ukpoliceonline.co.uk/index.php?/topic/41643-on-the-spot-fines-for-foreign-drivers-work/

http://www.policeoracle.com/news/On-The-Spot-Fines-For-Foreign-Drivers-Work_23264.html

I wonder what happens if you get a ticket when a non-resident? For example, driving a rental car when on vacation. I presume the ticket will go to the rental car company who will then pay and charge you (plus a nice service fee no doubt...). But is the rental car company required to send in a photocopy of your license with the fine?

We got a camera speed ticket in Wales in a rental car in 2008, and Avis charged my rental credit card for it, and sent me the bill. £85.  Most rental car places you do have to sign something that says you will pay any fines you get.  Although I rented a car in Geneva that I took to Milan once, got a parking ticket in Milan (albeit back in 2001), and when I asked Avis in Geneva about how I pay, they laughed and thew it out!