The pair opened the show with Chris bouncing in his seat, before revealing to the nation that Alex had said yes to her New Zealand born boyfriend Charlie Thomson. He then congratulated Alex, who couldn't stop smiling.
Earlier in the day Chris had suggested that Alex could be announcing an engagement during the show on Friday, revealing on his BBC Two Radio breakfast show that there could be "some news" about his colleague, adding that it was the "second most exciting thing that could happen to a girl".
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Chris Evans hinted that Alex Jones is engaged to her boyfriend Charlie Thomson
The 48-year old, who co-presents the show with Alex on Fridays, was discussing the upcoming Wales v England Six Nations rugby match on Friday evening. Talking about different nationalities of their guests, Chris said: "And then we've got Alex, who is very, very Welsh, of course she is, she's the cracker from Cardiff, the wonder from Wales, and then we've got her current boyfriend – current boyfriend – Charlie, who is a Kiwi.
"However, tonight on The One Show there will be some huge news of Alex Jones. And all I'm saying it's huge news for a girl, huge news for a boy, it's huge news, but for a girl it's probably like the second most exciting thing that could happen to a girl. It's happening to Alex.
"It's not in the script but she has asked us to talk about it tonight. So it's the easiest way of announcing it – I mean we are half way there as it is I suppose. So tonight's rugby is going to be the rugby and then overtly a celebration about something else."
Chris hinted that his co-host will make the announcement on The One Show
Alex has been dating her insurance broker boyfriend for three years. With Chris' suggestion of an announcement it appears that the couple are now set on building a future together, however the 37-year-old has previously admitted that she has not always been certain where their relationship will go, because Charlie's family live in New Zealand.
"The problem is he's from New Zealand and had been living in the UK – but was planning to go back home when we met. It's still an unresolved issue as to whether he will stay permanently.
"It's a big thing to ask him to give up his family and home for good. Obviously, we have a mortgage together now, which is a big commitment, but the issue of New Zealand is still there."