The primary objectives of this trial are (a) to demonstrate that the fixed-dose combination T40/A5 or the fixed-dose combination T80/A5 is superior in reducing blood pressure at eight weeks compared with A5 (b) to demonstrate that the fixed-dose combination T40/A5 or the fixed-dose combination T80/A5 is not inferior in reducing blood pressure at eight weeks compared with A10 and (c) to demonstrate that the incidence of oedema on the fixed-dose combination T40/A5 pooled with the fixed-dose combination T80/A5 is superior (less oedema) to A10 in patients who fail to respond adequately to six weeks treatment with A5.