3 is celebrating its one millionth European mobile broadband customer.
The firm has reported a "phenomenal" response to offers launched late last year, as many consumers supplement or replace their fixed line contracts.
Announcing the milestone, the broadband provider took the opportunity to draw attention to the high cost of data roaming charges for those using mobile broadband abroad.
"For many customers, it is their first personal broadband connection," said managing director for European telecoms at parent company Hutchison Whampoa, Christian Salbaing.
He continued: "However, due to the high wholesale data roaming costs charged between mobile operators in Europe, it remains very expensive for consumers to use mobile broadband while travelling abroad and roaming onto other networks."
Some networks are reported to be charging around £9.50 to watch a three minute YouTube clip or up to £142 for an hour-long TV programme.