AFTER 38 years in the Natural History Museum's iconic Hintze Hall, it's time for visitors to bid a fond farewell to Dippy the Diplodocus.

Yep, the 26-metre-long star attraction, whose replica skeleton arrived in 36 packing cases back in 1905, is to be replaced by that of a huge blue whale, which in turn has been gathering dust in the museum for more than 100 years.

But all is not lost, for the beloved plaster-cast dino - which has nabbed roles in films including Paddington and Night at the Museum 3 - is set to inspire a new generation as it travels the length and breadth of the UK from early 2018 to late 2020.

And its first stop will be at Dorset County Museum in Dorchester next year.

Making the switch, however, has proved something of a mammoth task - and to document just how super-sized it is, BBC Two's Horizon has spent two years filming behind the scenes footage for a one-off show, Dippy and the Whale. And with Sir David Attenborough narrating, viewers are in for a fascinating ride.

Here are some fascinating facts about the bold move...

*Since the Natural History Museum opened in 1881 it has welcomed more than 600 million guests through its doors, and the team of conservators and engineers weren't about to let the 'small' task of renovating the hall, where Dippy's 292 bones were taken apart one-by-one, infringe on the fun. In fact, all of the work was carried out without closing the museum to the public.

*The controversial decision to move Dippy didn't go down well at all, but Richard Sabin, the museum's Vertebrates Collection Manager, is convinced critics will be silenced when they see the skeleton of the world's biggest animal - and one of its most endangered - positioned hanging in a lunge diving pose in the great entrance.

*Dippy's colossal replacement - which as yet has no nickname - is the genuine skeleton of a young, female blue whale who was found mysteriously beached in Wexford, Ireland, back in 1891. The specimen was sold in its entirety at auction for £111, with its skeleton later acquired by the museum for £250 under the premise it was clean and ready for mounting.

*Horizon: Dippy and the Whale will air on BBC Two on Thursday, July 13.