The Government will "tackle" the high cost of some of their helplines, as bans on expensive 084 and 087 numbers go forward, according to a consumer campaign group.
Head of campaigns for Which? Alex Neill dubbed the initial ban "a huge victory" for consumers:
"Actually, what we have heard from the Government is that they are going to tackle this. They have said it's out of order. So we would expect them to lead by example and make sure they issue guidance to public bodies not to do this."
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Among those expected to attend the ceremony will be former US President Bill Clinton and ex-Northern Ireland first minister Peter Robinson.
Five people have been killed and 40 injured after a car and knife attack in London on Wednesday.
A wet, wintry night in places with rain and hill snow slow to move away from southern Scotland and northern England.