** Shares of Rightmove RMV.L, Britain's biggest property portal, up 5% at 450.3p
** Stock top gainer on the FTSE 100 .FTSE index, which is up 0.37%
** Co reports underlying annual operating profit of 297.7 mln pounds ($401.75 mln) vs 273.9 mln pounds a year earlier, in line with analysts' expectations
** RMV announces share buyback of 90 mln pounds
** CEO Johan Svanstrom says, "looking ahead, we will introduce a Rightmove app-in-GPT on OpenAI in the near future"
** YTD, stock down ~17.47%
($1 = 0.7410 pounds)
(Reporting by Ankita Bora in Bengaluru)
((Ankita.Bora@thomsonreuters.com))