High-redshift D/H values as a function of metallicity ([O/H] or [Si/H]). Our measurement towards CTQ 247 is shown as a red square. The red dotted lines (resp. vertical dashed lines) represent our constraint on (D/O) (resp. [O/H]). Other measurements from the literature are shown as filled circles. Grey filled circles have cautionary remarks in the text (from left to right: Srianand et al. 2010; Crighton et al. 2004; Pettini & Bowen 2001). Green stars represent HD/2H₂ measurements. The blue stripes represent the 1σ and 2σ prediction on (D/H)_p from Coc et al. (2012) using standard BBN and Ω_bh² from WMAP7 (Komatsu et al. 2011). The horizontal dotted line represents the primordial value proposed by Olive et al. (2012), see text.