The couple, who ended their five-year on/off romance in June, have secretly reconciled and Lewis plans to pop the question in 2014, as he has now got her mother Rosemary Elikolani's permission.
A source told Yahoo! OMG!: ''Lewis chose a glamorous, very feminine ring for her months ago from a well known designer, setting him back a five-figure sum.
''He's planning on proposing in the New Year by getting down on one knee, it'll be very traditional, he's even discussed it with her mother and told her his intentions.
''Lewis knows it'll look terrific on her finger and that she'll say 'yes' after all they've gone through. He wants their romance back and is going to put his heart and soul into cherishing her and making her happy.''
Nicole, 35, and the 28-year-old Formula 1 racing car driver have had a number of break-ups in the past, and although their split was rumoured to be because Nicole was keen to start a family while Lewis wasn't, he now wants to settle down as he has realised his life isn't the same without her.
The source added: ''He has climbed down from his rigid stance of being too young and too much of a traveller to marry and start a family.
''He's been saying that without Nicole life doesn't have the same meaning. They can't be without each other, they're soul mates.''
Lewis found it difficult being without Nicole following their split and doesn't want any ''emotional turmoil'' while Nicole is said to have agreed to quit the 'The X Factor' to help make their relationship work.
The source added: ''Lewis wants her beside him this year, he can't afford any emotional turmoil and they're missing each other, especially Lewis.
''Both of them have benefited from their split, but they've realised it's impossible for them to be without each other or interested in anyone else.''
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