ASP.NET MVC Model Binder returns null object

I am having a problem where everytime I post a form back to the [HttpPost] version of my controller action, the ModelBinder returns a null object. I can't work out why. If I change the signature to use a FormCollection instead I can see that all the correct keys have been set. Can someone help me pin point what's wrong here, because I can't spot it.

Here are the models for working with my views

public class DeviceModel
{
    public int Id { get; set; }

    [Required]
    [Display(Name = "Manufacturer")]
    public int ManufacturerId { get; set; }

    [Required]
    [Display(Name = "Model")]
    [StringLength(20)]
    public string Model { get; set; }

    [StringLength(50)]
    [Display(Name = "Name")]
    public string Name { get; set; }

    [StringLength(50)]
    [Display(Name = "CodeName")]
    public string CodeName { get; set; }

    public int? ImageId { get; set; }
}

public class DeviceCreateViewModel : DeviceModel
{
    public IEnumerable<SelectListItem> Manufacturers { get; set; } 
}

Which I use in my controller like so:

public ActionResult Create()
{
    DeviceCreateViewModel viewModel = new DeviceCreateViewModel()
                                            {
                                                Manufacturers = ManufacturerHelper.GetSortedManufacturersDropDownList()
                                            };

    return View(viewModel);
}

[HttpPost]
public ActionResult Create(DeviceModel model)
{
    // if I check model here it is NULL
    return View();
}

And the view looks like this:

@model TMDM.Models.DeviceCreateViewModel

<script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script> <script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script>

@using (Html.BeginForm()) {
    @Html.ValidationSummary(true