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In the aftermath of the technical hitch, the mobile phone operator pledged to compensate those affected by the outage and today it gave details of the money available.

In a statement, O2 said every UK customer would benefit though it remained unclear what estimate it was putting on the cost.

It said: "To thank all our customers for supporting us through an unprecedented and difficult period, we are...giving everyone on O2 a £10 O2 voucher to spend in store."

That would, on paper, set the company back by £230m in lost revenue.

The company said this offer would be redeemable via the O2 Priority Moments app or online.

Those people it identified as being directly affected by the failure to connect to its services would also get the "equivalent of three days back for the disruption as a gesture of goodwill and to say sorry."

Pay Monthly customers would receive 10% off their July subscription which will be applied on their September bill.

Pay & Go customers would get 10% extra on their first top-up in September, O2 said.

In the update, the company did not go into more detail about the glitch, which first appeared last Wednesday afternoon, but said all its subscribers - including business customers - would be contacted by Friday July 27.

As services returned to normal, chief executive Ronan Dunne told Sky News he was "embarrassed" by the network fault and worried about the potential for a backlash.

He blamed the disruption on "a piece of network hardware which manages the registration of handsets" and insisted such an issue was extremely rare.

Tesco Mobile customers affected by the outage are also in line for compensation.

A spokeswoman told Sky News: "Last week our customers experienced problems making and receiving calls, sending texts and using data over a one-day period.  This was due to a fault with one of the O2 network systems.

"It was a highly unusual and unprecedented situation.  However, we recognise the inconvenience and frustration felt by those affected.

"As a gesture of goodwill and to say sorry, we are giving our customers the equivalent of three days back for the one-day network disruption."