Updated at 15:15 on 25 Apr 2017 BST
More share price information
Please note that in order to view this video you need a web browser that supports HTML5 video.
Alternatively you can use the links below to view the video in your player of choice.
| video/mp4 (1704 kbps)
| video/mp4 (900 kbps)
| video/mp4 (452 kbps)
Back to top