BNP Chairperson Khaleda Zia left Dhaka for the UK on Saturday evening to receive medical treatment and spend time with her family members there.
She flew to London by an Emirates Airlines flight at about 7:35pm.
The BNP chairperson's personal assistant Abdus Sattar and her party's young leader Tabith Awal are accompanying her, reports UNB.
Senior BNP leaders, including its secretary general Mirza Fakhrul Islam Alamgir, standing committee members Khandaker Mosharraf Hossain, Moudud Ahmed, vice chairman Abdullah Al Noman and senior joint secretary general Ruhul Kabir Rizvi, saw her off at Shahjalal Airport.
BNP secretary general Mirza Fakhrul Islam Alamgir said their chairperson is going to the UK to receive her eye and feet (arthritis) treatment.
Asked when the BNP chief may return home, Fakhrul said it depends on how much time it takes for her treatment.
However, a BNP leader close to Khaleda said she may return home from the UK after celebrating Eid-ul-Azha there with her family members, including her eldest son party senior vice chairman Tarique Rahman who has long been living there, unless there is no major political development here.
Earlier on September 16, 2015, Khaleda Zia went to London for her eye treatment. Though it was a two-week tour, she returned home on November 21 of the year after celebrating Eid-ul-Azha there with her family members.
The emirate flight will have a stopover for two hours in Dubai at midnight and it is expected to reach London on Sunday morning, said Khaleda's press secretary Maruf Kamal Khan Sohel.
Several hundred BNP leaders and activists gathered at the nearby roads of the airport to see her off, forcing law enforcers to intensify security measures by blocking the airport entrance.
Ahead of her UK tour, the BNP chief sat with her party's standing committee members, the highest policymaking body of it, on Thursday night at her Gulshan residence, and gave them necessary directions to look after her party and sincerely carry out its organisational activities, including ongoing membership collection drive, party grassroots overhaul and next election preparation.
A leader of BNP's UK chapter said Zia family will have a reunion after nearly two years in London as Khaleda will stay at the residence of Tarique Rahman where his wife, daughter and late brother Arafat Rahman Koko's wife and two daughters reside.
Though it is the BNP chief's personal tour, he said the UK chapter BNP leaders, Bangladeshi expatriates and some UK's ruling and opposition parties' leaders are likely to meet her.
BNP insiders said the party's many major decisions regarding next election, candidate selection, and the party's next course of action will be finalised in London as its two top most leaders will stay under the same roof for a long time.