Interview process
Online tests before the phone interview. Phone interview had standard competency questions lasting about 25-30mins.
In face to face, 2 interviewers were present; one from the HR asking competency questions and the other a Senior Engineering Manager asking more engineering related questions.
Questions by the HR were pretty basic standard questions such as "Why do you want to work at TfL and why this role?", "Tell me a time when you done 'xyz', what was the situation etc etc?".
Questions by the Senior Engineer were more of situational questions which engineering related problems which are pretty straight forward in all honesty as long as you know your stuff. Format was pretty much, the HR and Senior Engineer took turns to ask a question and asked maybe about 5 each.
There was a presentation at the Assessment Centre which you get given a brief a week before to prepare (I only got mine a day before as they had first sent a brief a week before and got an email saying ignore that one we'll send a new one. With the weekend in between I waited but never got it so emailed them 3/4 days before, no reply. So I rang 2 days before and they sent it a day before the actual assessment day - others had got a week to prepare! They did say that they'll note it down and let others know so they can assess me accordingly, however when I was being asked questions in the Presentation by the Senior Manager I later found out that he wasn't told that I only had a day and not a week since when he asked very deep into detail questions I mentioned having just a day and not a week like others and he was like "Really? I never knew that." and the HR then try to cover up saying "Yes I was told" although the main questions being marked on at the presentation were from the Senior Manager as the presentation was Engineering related.)
Group exercise was fairly straightforward which at the end you have to write a report individually which is an email replying back to your manager based on the things discussed in the group meeting.
There was a exercise called 'fast-track' which is a problem solving exercise with 5 problems and 30mins to complete - I don't think anyone on the day managed to complete all 5 so it's quite difficult to complete within the time (they send you an example a week before, however it way too simple compared to the actual one, can complete that 1 problem in like 30seconds!)
Most difficult question
For a given situation in the presentation I was asked; "Which technologies would you use to solve these problems?" (which was pretty easy to answer!)... then they follow up asking "How does this technology actually work? What goes on inside the system so it works how you want it to?" (Quite difficult)
Interview tips
For the presentation, make sure you are given the full week - if not then contact them straight away and tell them to send it!! As many people that had a full week still found the time they had way too less to prepare! In the 'Fast' Track' don't complete the problems in the order they are in, as at the start you think that all problems have the same number of cards with information, but the ones near the end have less cards with less information and therefore are easier to complete correctly! For the interview, make sure you are aware between the differences of electronic and electrical engineering and also make your mind up as to which role you would want to do! Electrical consists on working on the underground transport, electronic consists of ITS Technologies and the overground transport such as buses of TfL, DLRs, as well as helping traffic flow of other transports such as cars and bicycles!
Experiences at the assessment centre
Presentation which you get a week to prepare for (well you should anyway!) and you present on the day - 10mins presenting, about 15/20mins questions.
Interview which last about 30/45mins with HR and Senior Engineering Manager.
Group task which you get 30 mins for, followed by individual report which you get 20/30mins for.
'Fast Track' problem solving exercise which you have 30mins to complete (maybe the hardest thing on the day!).