Increasing wheat yield is a key breeding objective, in terms of profitability and production sustainability with a growing world population. Yield is however a complex trait. It is the result of the interaction between the environment, developmental processes and a number of yield-related components, such as grain size and per spike number and number of tillers. In order to dissect these components and their environmental dependency in the UK, a bi-parental double haploid winter wheat population was created between parental lines with contrasting yield determinants. One parent (Oakley) achieves its yield through a high number of grains per ear, whereas the other (Gatsby) has fewer grains per ear, but a larger number of ears per plant. This elite pre-breeding population has been, and is being, assessed over multiple UK growing seasons. In-depth phenotyping has measured variation in traits including grain yield, grain dimensions, tiller number, plant height, flag leaf dimensions, date of key developmental stages, ear characteristics and canopy expansion and senescence. Trait heritabilities ranged from 0.28 to 0.91, and traits showed a wide range of correlations with yield. QTL detection using the Axiom 35k Breeders’ array is the first step to identify markers for these traits of interest which could be used for selection in breeding programmes. Meta-analyses of the phenotypic data across seasons reveals the scale of genotype x environment interactions and will inform the development of accurate genomic prediction models for testing within related UK breeding populations to accelerate genetic gain for yield.